On the other hand, I also feel that it doesn't hurt to if you deviate from your own rules sometimes, instead of being all fundamentalist about it.

I try to live by a whole set of self-imposed rules because I think they are beneficial to my health and well-being, but for me these are not dogma's. By default, I don't drink during weekdays for example, but if there's a special occasion once or twice a month, I don't feel guilty deviating and/or making up for it some other day. As long as you feel comfortable with it yourself.