Know thyself?

Socrates is famous for believing in the principle "Know Thyself".  The trouble is we have learned that it is nearly impossible to know yourself.  You can know lots about yourself but some important operating and governing parts of oneself don't talk.  They work in silence.  Sure, you can know quite a bit about what you did yesterday or last time.  But this is a new day, a new time, you are older.  You have more experience, you have aged a little, you have forgotten some things, so this time may be similar but it is not identical.  You may no longer be in pain.  You may remember what you did last time and be determined this time will be different but not know how.