Yesterday is gone

Perhaps it is Monday.  Perhaps I am tired.  Perhaps it is because another year is nearly gone.  I don't know the cause.  I am reminiscing.  I really wish I had all my current knowledge and experience when I was 18 or even 21.  I think there are a few more things I would attempt.  I think I would stay up all night a little more often.  I know my career path would have changed.  I would buy more things with cash.  I would worry less.  Again Perhaps it is just Monday talking.
Or perhaps I just have a case of the Mondays. 
Note if you don't know where that line originated I can't help you!