Al-Quran

وَمَا كَانَ قَوۡلَهُمۡ اِلَّاۤ اَنۡ قَالُوۡا رَبَّنَا اغۡفِرۡ لَنَا ذُنُوۡبَنَا وَاِسۡرَافَنَا فِىۡۤ اَمۡرِنَا وَ ثَبِّتۡ اَقۡدَامَنَا وَانۡصُرۡنَا عَلَى الۡقَوۡمِ الۡكٰفِرِيۡنَ

Surah Al-Imran - Ayah No. 147

There are some important instructions for Muslims in this dua of Surah Al-Imran.

 Firstly, the work of a realistic believer is that no matter how great a good deed he is doing in the way of Allah, he does not have the right to be proud of his actions, because his actions are also the grace and mercy of Allah Almighty and without Allah's grace no good action can take place.

Apart from this, no matter how correct a good deed a person does, it is not within his power to do it in accordance with the glory of Allah, so there is a need for forgiveness even while doing the good deed,

And this also cannot be a satisfaction that the good deed he is doing at this time will be a blessing for him in the future, so regret for the shortcoming in the present action and supplication for continuing it for the future should be the duty of the believer. 

 In the above mentioned prayers, the first thing is to ask for the forgiveness of one's past sins, indicating that the sorrow and grief that a person experiences in the world, or any suffering or defeat against the enemy, is often the effect of his previous sins , whose remedy is forgiveness and repentance.