I have to say, I do feel better when I get in my morning exercise even though it's only about 15 minutes. It can be hard to push yourself to do it when you feel craptastic otherwise, but it's usually worth it.
The key, I think, especially for people who don't exercise regularly is to start very slow. I started out with just 5 minutes a day every day and have slowly built up from there. At the moment 15 minutes seems to be my max before I tire myself out for the day, but morning yoga and stretching with the Wii Fit loosens me up, helps with some of the stiffness and joint pain, and wakes my brain up.