I find that when I'm really busy or feeling tired, I lose motivation to get myself to the gym. But EVERY time I push myself and go, I feel re-energized afterwards and am glad I did. So, when you're having a rough day and don't feel like putting in the 'effort' to go, I strongly recommend you push yourself, even if it's just for 20 or 30 minutes - you'll actually FEEL BETTER afterward and be more focused so you can do what you need to do more efficiently. Just my take, but it works for me. See you at the gym!