I sometimes think you may overbook and overschedule yourself because you have a core belief that relates to success, failure, and who you are. I don't know *what* the core belief is, just I have some sense that you aren't comfortable being a 100% success, so you add enough things to your schedule that you're likely to have some level of "failure" someplace, and that this somehow meets some need of yours, and fulfills your "story" of what your life is supposed to be like.

(feel free to examine my perceptions, and discard them if they don't seem to fit)