If you're feeling down, ask yourself "what's wrong with this moment?" Chances are that you're upset about something that happened in the past or you're anticipating something that might happen in the future. But is there anything wrong with this exact moment? Probably not. So stop worrying. And if there IS something wrong with this exact moment, there's only 3 things you can do to fix it: remove yourself from the situation, change something or accept it.