How can I mentally prepare myself for an important 1,500 m erg test? I need help pushing myself?

Ok, so I am a freshman novice rower. I'm not the best, but I'm not the worst. I really want to do well on our upcoming erg test, since it will affect placements at our first regatta. I have a hard time trying to push myself to give my all. I put alot of work in, but I dont think I am doing as well as I could because of not pushing myself hard enough.