“BE FIRM IN YOUR SUPPLICATION”
The Messenger of Allah (sallAllaahu ‘alayhi wa sallam) said:
“When any one of you invokes Allah (for something), he should be firm in his supplication and must not say: “O Allah, give me (such-and-such) if You want to,” for nobody can force Allah to do something against His will.
[Musnad Ahmad, Vol 3.p.101]
Note: Instead one should show resolve, being sure that Allah will certainly answer his supplication. By demonstrating such determination he shows that he places his trust in Allah, who can do whatever He wills without being prevented by anyone or anything in the heavens and the earth.