I know how that feels. I had a huge high the other day thinking that everything was going swimmingly and then all of a sudden my whole outlook changed in what it seemed like a moment. Wouldn't say I'm depressed, but man am I getting used to changing moods. I feel like if I had a mood ring the damn thing would be broken as many times as I've gone up and down. There's a good song you should listen to, it's called "Don't try suicide," by Queen. Very good and inspirational. Also sometimes it's best not to do anything and let the body rest. I've have been doing that more than anything the last few months and trying to get back on track... I've also been working somewhat which keeps my mind active and doesn't let me wallow in my self pity. I hope you get better.