The next installment of my "What I wish I knew before I started lifting" series ....
When I first started lifting weights, I thought I'd burn a lot of calories during my workouts. I didn't. Nobody does. The average person in a hour of weight lifting only burns between 150-300 calories. So you're thinking, "I just spent an hour at the gym, so I can get a juicy hamburger right now." No. That's not how it works. While weight lifting burns more calories than sitting on your sofa, you would have burned more calories by simply going for a walk. The average person doing mildly intense cardio is burning more calories than they are in the gym. So just because I'm going to the gym doesn't mean it's burning off that extra bag of Doritos I had last night before going to bed.
I never realized until recently that weight lifting didn't burn off many calories. What lifting will do is increase your RMR (resting metabolic rate), meaning that your body will be conditioned to burn calories day and night.