So you're having bouts of depression... Why do you want to listen to mellow music?
This isn't really an album reccomendation, but rather a band.
I see you're in St Louis,
Devnul. If only I had found this thread a few days earlier, I would have reccomended that you go and see Cowboy Mouth in concert, they were there just a few days ago, on the 30th of October, in Colombia I think it was... (is that close?)
Anyway, No matter how shitty I am feeling or tired or whatever, I always end up with an increased energy level of about 50x from before the show started. They put out so much energy during their live shows that you can't help but feeling great after you leave. It's an amazing natural high you get and any explination really doesn't do them justice if you haven't seen them in person. You just have to go and trust me on this.
Short of seeing them in person, I would reccomend their album "All You Need Is Live".
If you can't see them in person, then this album comes the closest to delivering that amazing energy and uplifiting feeling that you would otherwise get.
Off that album, or more specifically, listen to the song "Jenny Says" and if you're on Kazaa look for the "Live from the X-Lounge" version. It does wonders for your mood.
As Fred says, "I don't care What's bugging ya, I don't care what's bringing you down, whether it's your job, your boss, your school, your husband, your wife, your boyfriend, your girlfriend, your landlord... I don't care what it is, I want you to take all that frustration, all that anger, all that negativity, roll it into a tiny little ball, throw it in the air and just LET IT GO, LET IT GO, LET IT GO!"