My depression was lifted dramatically, but not by anti-depressants (I had a hormone issue), so for me a bunch of symptoms went away at once and in it's place I felt normal, effortlessly happy more frequently, and life just wasn't as hard - I felt more motivated to do things, I didn't need weeks of recovery after a stressful event, I didn't need a weekend of social isolation after going to a grocery store. I had less of a tendency to need or crave simple rewards, like food or video games. Food became less necessary as a reward, and my behavior towards food became less obsessive.
There was a sense of feeling so "normal" and like what you imagine other people must feel like. You start to understand why your colleagues and others in your life don't seem to be struggling so much, how they can fit so much into their lives.
I didn't really understand depression until these experiences - I thought what I experienced was just normal up until then, and blamed myself for being lazy or grumpy or ill-tempered by nature, rather than suffering from depression and other issues.
I have taken buproprion before, and it made me have mood swings where I became manic and filled with energy, then inevitably I would crash and feel awful. It also gave me TMJ from all the extra grinding my teeth were doing, so I had to quit (so painful!).
I'm not sure I'm old enough to answer this, but retirement scares me, and I basically don't know if retirement is financially likely or reasonable. Even if you invest enough into a 401k early enough, you have a pretty good chance of having serious health problems at some point in life that will probably take most of that money.
Basically the situation is bleak, so I try to focus on doing what I can to improve my situation without dooming about what I can't control.