I can't speak for the GP, but I've found (as a student), that writing down the things I have due or have to accomplish by a certain date on my calendar frees up a lot of mental energy.

I'm not a big fan of todo lists, but I am a proponent of keeping yourself organized. By writing things down I stop worrying about forgetting to do something. Of course, that's not the same as a todo list. Usually I just look at my calendar each morning and pick 2-3 things to get done for the day. That way I get the benefit of focusing on only a few things while having the peace of mind of knowing that I'm not missing anything important.