The strong believer is better and more beloved to Allaah, than the weak believer and there is goodness in both. Strive for that which will benefit you, seek help from Allaah and do not despair. If a mishap should happen to befall you then do not say: If only I had acted...such and such would have happened'. Rather, say:
قَدَرُ اللّٰهِ، وَمَا شَاءَ فَعَلَ
It is the Decree of Allah and He does whatever He wills. 
Qadarullaahi wa maa shaa'afa'ala.
...for verily 'If' lets in the work of the devil. Indeed Allaah (Subhaanahu wa Ta'aala) rebukes due to negligence and slackness, but take to determination and caution, and if a matter should overtake you then say:
حَسْبُنَا اللّٰهُ وَنِعْمَ الْوَكِيْلُ
Allaah is sufficient for me, and how fine a trustee (He is). 
Hasbunallaahu wa ni'amal-wakeel.