If you don't keep a written record of the game, you can't claim a draw by repetition or the 50 move rule. Also, how would you prove that your opponent was cheating if he just took one of your pieces off the board? It is absolutely essential to keep score and not at all difficult with a little practice. Listen to your coach, that's what he's there for! Everything he says is for your benefit, no his own.

I don't even have a clock most of the time. When I do, I like a 60min clock.

How can you record and learn from your games without notation?  I like a 90 minute clock.

When I play I like a 40 minute clock.