How to be sure I give it my all today?

We have a guaranteed 2 games with this team, which we are able to beat, but we let them get easy goals. We usually lose by a goal, or win by two. I'm a center but I want to know how to save my energy for when I really need it. I always go hard, which isn't a bad thing, but when should I get off and who or where should I cover during this game. This team's defense can slap the puck from the blue line, so should I stay in the middle of them or stay on one?