I didn't do this with alcohol, I've always enjoyed alcohol but drugs... absolutely. I'd think, "it's been a while, no harm in partying once." Two weeks later, hating myself and hating how I felt, and hating everything about the situation, I'd be at my dealer's house for the 6th or 7th time. After months away from it the taste when I smoked made me vomit and I'd do it anyway. Simply watching friends snort meth made me gag, but I'd grab a straw.
I have trouble with the social aspects of alcohol. A few weeks ago I attended a banquet with 350 people and I saw 4 who weren't drinking. It made me horribly self-conscious about not drinking, so I went to the bar and ordered a tonic water with lime so it looked like I was drinking. I really don't think anyone else cared but it made me feel a lot better.