i'm going to butt hurt most of the forum (what else is new) but you don't need to feel great to get in a weight training session. it isn't like you are running a marathon or doing a triathlon or playing in a professional sport like football, soccer, or hockey which takes you being at the top of your game to perform well.
weight training isn't even close to any of those so don't make the excuse that you are too tired to do it or you are only short changing yoruself