A big problem is that your mind keeps reminding you of things when you can't do anything about them. It has no sense of past or future. That means as soon as you tell yourself that you might need to do something, and store it only in your head, there's a part of you that thinks you should be doing that something all the time. Everything you've told yourself you ought to do, it thinks you should be doing right now. Frankly, as soon as you have two things to do stored only in your mind, you've generated personal failure, because you can't do them both at the same time. This produces a pervasive stress factor whose source can't be pinpointed.