I am going to be brutally honest with you. It really depends what the sin is. Some sins we can give to much weight to, i.e. we can think God is heavy on us when he is not. I am going to lay down some guidelines based upon the bible and what I would call experience.
Sexual guide lines:
If your sin is masturbation, yes it is a deviation from God's best, but few men really, Christian, or not, ever really over come it. In my opinion, God will not judge you for it. The pressure that builds up in a man sexually has a release valve, and whether this occurs through masturbation, or a wet dream it will occur.
Pornography - should be avoided at all costs, the bible tells us that when we "look at a woman to lust for her, we are committing the act in our hearts". Practice purity in this area. I know you may find yourself thinking of a woman when Masturbating, it is likely, but still avoid the use of porn, the whole industry is full of sin.
Actual sexual sin - having sex outside of marriage, again must be avoided at all costs.
Sorry for the graphic content, but I hope it helps.