STRONG BELIEF AND CONDUCT H 101 "A strong believer is better and more loved by Allah than a weak one (and in both there is good). Out of all good things desire that which is most beneficial for you. Keep supplicating to Allah for help and do not give up. If you are afflicted in any way, do not say: 'If only I had done this and that things would have turned out differently.' Instead say: 'Allah has written and did as He willed.' The phrase: 'Had I only' opens the gates of evil conduct." R 101 Muslim with a chain up to Abu Hurairah who related that the Prophet, praise and peace be upon him, said this.
100- السادس : عن أبي هريرة رضي الله عنه ، قَالَ : قَالَ رَسُول الله صلى الله عليه وآله وسلم : "المُؤْمِنُ القَوِيُّ خَيرٌ وَأَحَبُّ إِلَى اللهِ مِنَ المُؤْمِنِ الضَّعيفِ وَفي كُلٍّ خَيرٌ . احْرِصْ عَلَى مَا يَنْفَعُكَ ، واسْتَعِنْ بِاللهِ وَلاَ تَعْجَزْ . وَإنْ أَصَابَكَ شَيءٌ فَلاَ تَقُلْ لَوْ أنّي فَعَلْتُ كَانَ كَذَا وَكَذَا ، وَلَكِنْ قُلْ : قَدرُ اللّهِ ، وَمَا شَاءَ فَعلَ ؛ فإنَّ لَوْ تَفْتَحُ عَمَلَ الشَّيطَانِ" رواه مسلم .