Just let them know that you were in really bad mood and not in your senses, and that you're sorry. That should straighten things out. It may take take them a few days but they'll forgive you.
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I'm going to have to readjust my sleep schedule as well, I've gone nocturnal too and I haven't gotten anything done since like... November. I'm also really nervous about school - I've got this irrational fear that I'll make a complete fool of myself or that no one will like me, and I can't seem to shake it. Guess I'll just have to wait and see what happens on Monday.