Moodiness and impatience are signs of bad character, and the symptoms of a person whose affairs with Allah are not quite right, and they may even be a sign of Allah’s displeasure.
وَمَن يُرِدْ أَن يُضِلَّهُ يَجْعَلْ صَدْرَهُ ضَيِّقًا حَرَجًا كَأَنَّمَا يَصَّعَّدُ فِي السَّمَاءِ ۚ كَذَٰلِكَ يَجْعَلُ اللَّهُ الرِّجْسَ عَلَى الَّذِينَ لَا يُؤْمِنُونَ
and whomsoever He (Allah) wills to send astray, He makes his breast closed and constricted, as if he is climbing up to the sky. Thus Allah puts the wrath on those who believe not. (6:125)
For the most part, moodiness and impatience are related to unmet expectations.
وَمِنَ النَّاسِ مَن يَعْبُدُ اللَّهَ عَلَىٰ حَرْفٍ ۖ فَإِنْ أَصَابَهُ خَيْرٌ اطْمَأَنَّ بِهِ ۖ وَإِنْ أَصَابَتْهُ فِتْنَةٌ انقَلَبَ عَلَىٰ وَجْهِهِ خَسِرَ الدُّنْيَا وَالْآخِرَةَ ۚ ذَٰلِكَ هُوَ الْخُسْرَانُ الْمُبِينُ
And of the people is he who worships Allah on an edge. If he is touched by good, he is reassured by it; but if he is struck by trial, he turns on his face [to the other direction]. He has lost [this] world and the Hereafter. That is what is the manifest loss. (22:11)
A believer should do his or her best to achieve what they want, but they must also know that it is not their efforts that make something happen. Allah says:
وَمَا تَشَاءُونَ إِلَّا أَن يَشَاءَ اللَّهُ رَبُّ الْعَالَمِينَ
And you do not will (something), unless (it be) that Allah wills, the Lord of the ‘Alamin (mankind, jinns and all that exists). (81:29)
So, expressing frustration with others (moodiness and impatience) is a sign of unwillingness to accept Allah’s qadar (pre-ordainment), which is a sign of ignorance, weak imaan or perhaps no imaan at all.
As a believer you should be fully aware that things are not always going to go your way. Allah says:
لَتُبْلَوُنَّ فِي أَمْوَالِكُمْ وَأَنفُسِكُمْ وَلَتَسْمَعُنَّ مِنَ الَّذِينَ أُوتُوا الْكِتَابَ مِن قَبْلِكُمْ وَمِنَ الَّذِينَ أَشْرَكُوا أَذًى كَثِيرًا ۚ وَإِن تَصْبِرُوا وَتَتَّقُوا فَإِنَّ ذَٰلِكَ مِنْ عَزْمِ الْأُمُو
You will surely be tested in your possessions and in yourselves. And you will surely hear from those who were given the Scripture before you and from those who associate others with Allah much abuse. But if you are patient and fear Allah – indeed, that is of the matters [worthy] of determination. (3:186)
A person’s inability to recognize and be thankful and grateful to Allah for all the good that they have will also contribute to his/her moodiness and impatience.
وَاشْكُرُوا لِي وَلَا تَكْفُرُونِ
And be grateful to Me and do not deny Me. (2:152)
كَذَٰلِكَ نُصَرِّفُ الْآيَاتِ لِقَوْمٍ يَشْكُرُونَ
Thus do We explain variously the Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) for a people who give thanks. (7:58)
Your inability to understand the above and make the necessary changes (in preparation for your unavoidable death) may be directly related to your sins, and your inability to admit to such sins.
If you wish to cure your moodiness and impatience, you must take yourself to account. ‘Umar (RAA) said:
“Take yourselves to account before you are taken to account.”
Then, start seeking Allah’s forgiveness, and perhaps He will have mercy upon you and cure you.
وَالَّذِينَ إِذَا فَعَلُوا فَاحِشَةً أَوْ ظَلَمُوا أَنفُسَهُمْ ذَكَرُوا اللَّهَ فَاسْتَغْفَرُوا لِذُنُوبِهِمْ وَمَن يَغْفِرُ الذُّنُوبَ إِلَّا اللَّهُ وَلَمْ يُصِرُّوا عَلَىٰ مَا فَعَلُوا وَهُمْ يَعْلَمُونَ
And those who, when they commit an immorality or wrong themselves [by transgression], remember Allah and seek forgiveness for their sins – and who can forgive sins except Allah ? – and [who] do not persist in what they have done while they know. (3:135)