Having a workout buddy makes me accountable not only to myself but my buddy as well. Since my love of running rubbed off on my buddy, she has come to expect my call at 5am to get her up and going. Those mornings I don't want to get up, I push myself knowing she's waiting for me.
Those 5am runs keep me energized all day; it's a great way to start your day. I get my exercise in early, so I can enjoy my eveings when I get off work. Working out with a friend makes the time go by quickly because we can catch up on what's going on in each other's lives.