Depression is easy to wallow in and hard to fight against, but if you just give in to it completely it's a downward spiral. You skip going to class because you're feeling depressed, then you stay in the rest of the day because you've already missed one class, then you skip the next class because you already missed the first one, and you stop answering your phone because people are asking whether you're okay and you don't want to talk to them, and it just gets worse from there. That spiral doesn't have to happen, and thinking in the right ways even though you're depressed is one of the big things that halts it.