Invocation for when something you dislike happens, or for when you fail to achieve what you attempt to do

“The strong believer is better and dearer to Allah, than the weak believer and in each of them there is good. Strive for that which will benefit you, seek help from Allah and do not falter. But when you are stricken by some setback, do not say ‘ If only I had done such and such’. Rather, say:

  ‘It is the Decree of Allah and He does whatever He wills.’

For verily the saying ‘If‘ (i.e. if only I had) begins the work of the devil.’

[Narrated by Muslim 4/2052]