If you are interested in some further reading on training check out Matt Thortons blog, who i train under.
Like others have said, few things focus me more than intense physical combat with another person. There are times when i go into class, everything seems to be clicking, and when grappling its like my mind is still and my body is just doing what its been taught. Those are usually the times when i do the best.
Grappling with a fully resisting opponent has a way of making alot of other things in life seem much easier. I imagine its similar with Muay Thai or any other striking art.
Give it a try, and let us know what you think.