It can be a self-sustaining cycle -- don't go outside because you're depressed, and depressed because you don't go outside. I've caught myself in it a few times, but when I do, I just try and push through the initial discomfort and force myself to hit the gym or go to a park or something. That's where lardie in the OP has failed and will likely continue to fail. They're unwilling to feel that tiny twinge of discomfort that comes with trying anything that requires a modicum of effort, like not eating everything in front of it.