In your simple world, I guess all an alcoholic has to do is confess his "sin" and he won't be drinking any more.
You know I would never say such a thing. My point was that when God forgives in confession and has the firm purpose of amendment (i.e.. has the intention not to sin again) one's sin is forgiven by God with the absolution of the priest. Should he repeat the sin he should return to confession but that doesn't mean that the sin of the previous confession was not forgiven. I need to go to confession at least once a week because I am weak and sin often and I believe God forgives me every time I receive the sacrament of penance. I need His grace.