The main idea is to figure out where yo uscrewed up. All those things you mentioned are just aids. Did you drop a piece to a knight fork, how could you have avoided it? Did you opponent slowly crush you by advancing a passed pawn? How could you have prevented him getting the passed pawn in the first place, or how could you have blockaded it better?
Did every move have a purpose/ a plan? was there a better plan? What were your opponents plans and how might you have better fought against them?
etc.