بسم الله الرحمن الرحيم
Ali Ibn Abi Talib (radhiyAllahu 3anhu) is reported to have said:
“Goodness is not in your wealth and offspring being plentiful; true goodness is when your [good] deeds are plenty and you have great understanding and forbearance, and when you compete to worship your Lord.
If you do good you praise Allah and thank Him, and if you sin you beg Allah’s forgiveness. There is no good in this life except with two types of men: A man who sins but then corrects himself through repentance, and a man who strives and hastens to get [the good] of the hereafter.” 
Ali ibn Abi Talib describes that true goodness is not and will not be found in the pleasures of this dunya but rather what you prepare for the hereafter. And the best of people are two and SubhaanAllah one post does not give justice to such a profound statement as there are many aspects of this one saying that should be covered. And for us to bi ithnillah, strive to be of those who have goodness in this life we need to understand what Tawbah is and its merits.
Linguistically At-Tawbah is defined as seeking repentance, renouncing that action and to make the intention to not return to that matter.
Islamically, it is the act of returning from acts of disobedience of Allah, Subhaanahu wa ta’alaa, to His obedience. Ibn Al-Qayyim (Rahimahullah) said:
“The true essence of tawbah is to return to Allah and to adhere to what He loves and renounce that which He hates- Tawbah is a journey from the disliked to the liked”
The action of Tawbah uncovers the heart from the darkness of sins and disobedience and illuminates and returns it back to its original, pure and sinless state. At-Tawbah awakens the heart from the slumber of negligence and uncovers the veil of darkness that envelopes the heart.
At-Tawbah Falaah! It calls to success, it leads to happiness and it not only expiate sins but, if it is perfected, it changes the sins into good deed. SubhaanAllah how Merciful Allah is! One of the most beloved acts of worship to Allah is when a slave turns in repentance to Him, seeking only His pleasure and forgiveness, with sincerity.
The Prophet (sal Allaahu alayhi wa sallam) said:
‘A believer sees his sins as if he is sitting under a mountain which he is afraid may fall on him. Whereas an evil, wicked doer considers his sins as flies passing over his nose and he just drives them away.’ 
Bilaal ibn Sa’eed said:
“Don’t look at any sin as being insignificant, rather, Look at the greatness of the one you disobeyed” 
At-Tawbah also has an effect on our ibaadah to Allah, it brings forth love, softness and gratitude to Allah, praises to Him. It opens our heart to being thankful for the many blessings He grants us. From the merits of Tawbah is humbleness and humility of the heart, submissiveness to Allah becomes our main concern. The more Tawbah a slave of Allah makes, the more beloved you become in His eyes. Why? Because the essence of uboodiyah is submissiveness and humility and this, ya ukhti ya akhi is the state you put yourself in when you repent to Allah. And that is why Allah is closest to His slave when he/she is in prostration to the Lord of the world. And as Dr. Saleh as-Saleh (Rahimahullaah) said “…this may be the secret behind the response of Allah to the invocation of the oppressed, the invocation of the traveller and to the invocation of the fasting person. Because of the humility in their hearts. The anguish of the oppressed causes the broken heart. Similarly the traveller finds broken heartedness (humility) when he travels to strange places. Similarly in a fasting person, it breaks the animalistic drive for lust & desires as Imaam Ibn Al-Qayyim (rahimahullah) discussed. Despite the greatness of Tawbah and its great blessings there are however mistakes made by many people regarding Tawbah. And that is due to ignorance or negligence and his heedlessness.”
“O you who believe! Turn to Allah with sincere repentance! It may be that your Lord will expiate from you your sins, and admit you into Gardens under which rivers flow — the Day that Allah will not disgrace the Prophet and those who believe with him. Their light will run forward before them and in their right hands. They will say: “Our Lord! Keep perfect our light for us and grant us forgiveness. Verily, You are Able to do all things.”
(Surah at-Tahreem verse 8)
Allahuakbar! Allah is calling on the believers! To make a sincere repentance that will erase the sins that preceded it and mend the shortcomings of the repenting person. Allah is encouraging and directing us to quit the evil that we do by describing the reward of Al-Jannah and then Allah says, “it may be” which means as Ibn kathir said, that He will forgive you. And then on yawmul-qiyaamah, on a day, when your Mother will turn away from you, on a day when your siblings will not be there to counsel you nor your father to protect you! On a terrifying day when only Allah, Glory and Might be He, is there…They the believers will say: “Our Lord! Keep perfect our light for us and grant us forgiveness. Verily, You are Able to do all things.’”
Mujahid, Ad-Dahhak and Al-Hasan Al-Basri and other said, “This is the statement that the believers will say on the Day of Resurrection, when they witness the light of the hypocrites being extinguished.” May Allah make us amongst the believers Ameen.
SubhaanAllah, Allah also says:
“Allah accept the repentance of those who do evil in ignorance and repent soon afterwards; to them will Allah turn in mercy: For Allah is full of knowledge and wisdom.”
(Surah An-Nisa: 17)
But keep in mind that Allah also said,
“Of no effect is the repentance of those who continue to do evil, until death faces one of them, and he says, “Now have I repented indeed;” nor of those who die rejecting Faith: for them have We prepared a punishment most grievous.” (Surah An-Nisa: 18)
It becomes too late to repent “when the angel of death comes forth and the soul reaches the throat, approaches the chest and arrives at the state when it is being gradually pulled out, then there is no accepted repentance, nor a way out of that certain end.” 
Repentance will not be accepted when the sun rises from the west, nor when the disbeliever dies in the state of disbelief and polytheism. “His sorrow and repentance will not avail him. Even if he were to ransom himself with the earth’s fill of gold, it will not be accepted from him. And for them there is a torment that is severe, eternal and enormous.”  May Allah protect us from such a punishment Ameen!
A Muslim is one who lives their life in a state between fear and hope, not being certain that he will enter paradise and fearing his sins. Despite the Sahabah (may Allah be pleased with them) being the most righteous of people and despite some of them even being promised paradise, they feared Allah and worshiped Him having a balance of fear and hope. Sheikh Muhammed Salih Al-Munajjid said regarding this that,“…the Muslim must obey Allah and repent and hope for the mercy of Allah, keeping in mind that He forgives and accepts the repentance of the one who turns to Him sincerely, so he hopes that Allah forgives him. He knows that Allah accepts and loves the righteous deeds of His slave, so he strives to do righteous deeds hoping that they will be accepted.
If he lives in this state, fearing his sins and hoping for the mercy of his Lord, he will strive to worship Him and keep away from sin, asking Allah to reward him for his righteous deeds until he meets Him when He is pleased with him, and he seeks refuge with Allaah from his heart being turned away or his situation changing, as the Prophet (peace and blessings of Allaah be upon him) used to pray, “O Controller of the hearts, make my heart steadfast in Your religion.”
Tawbah is a life transformational process and is the very step to abandoning the old ways and a step for us to replace those sins with righteous deeds. So be of the saabiqoon (foremost) in regards to pleasing Allah and turn away from this sin that is only furthering you away from the love and mercy of Allah.
“The right of Allâh is too great and heavy for the creation to fulfill and the blessings of Allâh are too many to enumerate, but you should remain repentant, morning and evening.” 
 Ibn ‘Askir, Al-Tawbah article 13
 Saheeh Bukhari Volume 8, Book 75, Number 320
 [Bayhaqi in Shu’bul-Eemaan, 5/430].
 Tafseer Ibn Kathir
 Talq b. Habîb (Allâh have mercy on him) collected in Ibn Abî Al-Dunyâ, Al-Tawbah article 62.
 Madaarij As-Saalikeen