We remember pleasure forever. We always seem to remember the good times when we have them. Believe me, I know that we had some good times with the effects of our substance. Whatever our substance was, there was a lot of times that we liked it.
On the flip side of that coin we also have a natural defense mechanisim that blocks out pain and we tend to forget the bad times. We forget the bad rather quickly but always remember the pleasure. It doesn't seem fair to one trying to get sober and clean.
Just hang on for the ride. A clean happy life is yours for the taking.