Try doing something new, often. You avoid stagnation, you learn skills, depending on what exactly it is you do you meet people, get fit, become a more interesting person. All of these things to do wonders for you, and life has more luster when you see more of it. Very hard to do when you're at your worst, of course, but for those that have the ability, I believe in it. Recently forced myself out of a rut by learning to make 3D stuff in Blender, didn't even have to go outside due to lots of good information online.