Resisting temptation..and drawing closer to the heart of God. Fasting and prayer go hand in hand.
I havent done an entire forty days without food exactly like Jesus did as not only did he do that he went into the wilderness to do so. It is harder to fast when around people because people expect you to eat with them as normal everyday life. But you can fast discretly but need to set aside time to do so and also act normally while you do so.
It actually prepares you do do what God wills like ministry. Because all that time you are fasting and denying the flesh you are thinking of God and being fed spiritually.