When I start telling myself that 10 minutes of exercise won't make a difference, I then say out loud, "it does more than ... sitting in front of the computer, sitting on the couch, eating that last whatever."
I'm thinking of my life as a rescue mission. How helpful can I be to my family, if I'm not as fit and healthy as I can be? Without good health, my reflexes are slow, and I can get sick often. Taking care of me first, makes me healthy first, and that makes me more helpful to those I love.