I think this is also why I have been having so much trouble with meditation/guided relaxation for the past several months. I try to quiet my mind, but my thoughts will not stop.
I'm not sure what to do about this. My primary thought is to continue to exercise, because when I am lifting weights or doing tai chi I am completely focused on what is happening in the present moment. In yoga and aerobics, I often look at the clock, so they aren't quite the same -- I don't really become entirely absorbed. (Unfortunately, it looks like the beginning tai chi class isn't going to happen, and the intermediate class I was willing to try is still on Tuesdays, when I have my Dreamweaver class.)
I thought about meditation, but I've had so little luck with quieting my mind lately that it seems like a goal to work toward, rather than a way to work on the problem.
I also thought about reading some more Thich Nhat Hanh, which has helped me in the past. I haven't been reading much lately, but maybe it's time to give him a try.
Perhaps it might also help to do what they teach in meditation: notice that your mind has strayed and gently bring it back to the present moment. So when I notice a desire to look at the clock, just gently bring myself back to what is happening in the room. I will try that today.