There is no such thing as an unsuccessful prayer.
Do you feel like your prayers are ineffective? Does it seem like they hit the ceiling and don’t reach heaven? Is praying an exercise in futility for you?
Don’t evaluate the effectiveness of your prayers solely on the basis of whether God gives you what you asked for. (He is not a celestial vending machine.) Sometimes He may respond in the way you asked; other times He may deny your request because it is not in your best interest; or, He may postpone action for reasons that are unknown to you. Regardless of His response, God hears your prayers and attends to them.
Prayer is not designed to give you everything you want. (God is not Santa, and prayers are not your Christmas gift list.) The purpose of prayer is to connect you with God. Every prayer is successful because it links you with God in a personal conversation.
Don’t worry about anything; instead, pray about everything. Tell God what you need, and thank him for all he has done.