You’ll often find that when you bring your mind to bear on a particular topic, perhaps studying some painful part of your life, that in some uncontrollable way your attention is interrupted; the mind jumps and skips the subject. You’ll think, “What was I thinking about?” and you can’t remember.
This is just how the mind works, and as dharma practitioners you must become accustomed to it. Ultimately, the mind is a machine and it can be trained to do anything. You must learn to recognize the interruption of attention and forcibly bring your mind back to the subject. This is the only way that you’ll begin to see all the reasons why you didn’t want to address the subject. This is how you process through a problem or an issue.