The problem of depression is that it makes incredibly difficult to do those things, getting exercise, eating better, sleeping well, anything that makes you feel

The problem of depression is that it makes incredibly difficult to do those things, getting exercise, eating better, sleeping well, anything that makes you feel better. That's why people use antidepressants, because they aren't well enough to start doing other things to help themselves. Your advice ultimately boils down to "just don't be depressed" and that has never worked.