With you on that. Good music helps, also changing your workout time and schedule. If you do it at the same time or every day, for me at least it gets boring. I like to do some days workout in the morning, shower or evening, shower. I never let it get in the middle of my day though.
Also making yourself a shake before or after you work out definitely gets me in the 'workout' mood. So is having designated workout outfits. I know it sounds really girly and stupid but honestly I work best that way.
"Strength is the ability to use a muscle without tension"