18. "Try harder!"
If there's one thing you can trust, it is that people who have depression are trying their hardest. All. Day. Long. Sometimes just getting out of bed can be a complete struggle for those with depression, as they feel as if they have no reason or drive to face the day. While it is easy to say "oh, just get up" it is harder to put yourself in someone else's shoes and discover the difficulty. If you cannot empathize yourself, at least do the person the courtesy of believing their story, and trusting that when they say they are trying - they are.
Alternative: Instead of telling someone to try harder, let them know that you acknowledge how hard they are trying, even at their low points when things don't seem to be working out. Life is hard, and it is way harder for those with depression - even when nothing else is wrong.