As college students, we are supposed to get more than 8 hours of sleep everyday yet very few of us actually meet these hours. Not only does a good night sleep improve your memory, it also enhances your focus. It might seem like a good idea to stay up until 2 am to study but this is actually counterproductive because you will need the energy you're burning away to concentrate and stay alert during your test.
Never feel pressured to do anything that you aren't comfortable with. You don't have to make up lies or excuses, you just have to be straightforward. The people who don't respect that don't deserve you.