I think one of the most powerful lessons that I have learned in over five decades of training (in both the martial arts and weight lifting) is that Movement is Medicine... and a powerful one!
The simple act of going to the gym and getting in a workout, regardless of how hard or long it is, always makes me feel and move better. I know that there are biological and hormonal reasons for this, but I think it goes even deeper than that. The primal act of using your body, sweating and straining, helps to clear out the cobwebs and reset you back to "normal". This is especially true after a frustrating day at the office... I NEED to get into the gym and work off a little (or a lot) of excess stress and energy that I've built up over the course of the day. There is also the fact that I really need to regain my posture and structural alignment from the damages of sitting all day.
BTW - I've never felt worse after working out. Tired - yes! Worse - NEVER!