Yoga in the morning -- whenever I miss a few days of yoga in the morning (particularly on the weekends because I try to get a bit more sleep) and then I get back to it I remember why I love it so much. It feels so incredible - just 10 or so stretches and I'm totally ready to face my day. It's worth waking up 15 minutes earlier just to do it.
I gave myself a writing target and told myself - if I don't hit it, I won't be allowed to go for my boxing lesson which will be the last one for this month.
Let me tell you, I worked frantically to hit that target, rushed like a maniac to get ready for the class, and then took out all my frustrations on the boxing pads.
I came home, drenched in sweat, pumped full of adrenaline, and right after showering I was back at my desk to work for a few more hours before dinner.
Do what you need to do to get it done. It's not always easy, but it is possible.