While exercising, you can make your experience much worse by constantly telling yourself things like, “This stinks. I wish I didn’t have to do this, I’d much rather be on my couch,” etc., OR you can make it much better by telling yourself things like, “It’s so great that I’m doing this. I deserve so much credit. I’m going to feel so much better when I’m done.” 
Remember, it’s not only what you do, it’s what you say to yourself while you’re doing it.