I got into shape because I took kick-boxing lessons every day to prepare for a fight scene with Taylor Lautner. I really wanted to lie down and eat Chinese food, but I kick-boxed every morning and ran. If someone was filming you with your kit off, you'd do the same thing.
Even if you're playing Brahms or a Beethoven concerto, you've got to have a different vantage point, slightly, each time.