If we abide in Christ, He will answer our prayers  -  John 15:7

If ye abide in me, and my words abide in you, ye shall ask what ye will, and it shall be done unto you.

Abiding in Christ is the requirement of a successful prayer life. The closer we are in fellowship with Him, the more we will know what His will is for us, the more we can rest assured that our prayers will be answered.