If you keep going back to the things that separated you from God initially, then you are not allowing God to forget your sins. God "forgets" our sins, in the sense that He does not remember them against us, He does not hold them against us, since we are forgiven. God wants to "forget" our sins.
This is why we need His salvation. He not only forgives us for the sins we have done, He empowers and enables us to live a life that if pleasing to Him.
2 Peter 2:20-22
(20) For if by a recognition of the Lord and Savior, Jesus Christ, they have escaped the defilements of the world, and again being entangled they have been overcome by these, then their last things have become worse than the first.
(21) For it was better for them not to have recognized the way of righteousness than having recognized it to turn from the holy commandment delivered to them.
(22) But the word of the true proverb has happened to them: "The dog turning to his own vomit;" also, the washed sow to wallowing in mud. Prov. 26:11
