If I regard iniquity in my heart, the Lord will not hear me (Psalm 66:18).

Prevailing with God in prayer is sacrosanct, and it's really what you need. But you see, if you're going to prevail with God in prayer, and have results from Him, then before you begin such prayer —whether for yourself, somebody else, or about any situation— the first thing is to repent of your sins, peradventure you've not been living right.

There're different kinds of sins that people commit; for instance, it can be the sin of pride and arrogance; if you don't repent of them, you can't prevail with God. The same is applicable to any other kind of sin. You can't prevail with God in prayer, because that sin will be in your heart, and like David said, "If I regard iniquity in my heart, the Lord will not hear me" (Psalm 66:18).

Isaiah said, "Behold, the LORD's hand is not shortened, that it cannot save; neither his ear heavy, that it cannot hear: But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear" (Isaiah 59:1-2).

Christianity is a walk in righteousness. You can't fellowship with God upon your sins; He's a just, righteous and holy God.
"My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous" (1 John 2:1).

You don't have to sin, but if you do, repent quickly, receive forgiveness and live right. 1 John 1:9 says, "If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness." His Word is a cleanser; it sanctifies and purifies your heart of sin and all unrighteousness. Give yourself to the Word. His Word is the true light to guide you always in the path of righteousness.