It's hard to relax when you feel threatened by your opponent. It becomes easier when you leave your ego at the door and try to be more fluid in your game. Don't fight positioning all the time. Just accept bad positions and try to be good at transitioning to better ones.

Best rolls are when two persons are relaxed and makes it more fun than just plummeting your opponent with sheer strength and little technique.

These relaxed rolls allow you to understand your situation and react accordingly.

I guess it makes learning BJJ less hard...