I concur and want to add a realization I had some time ago: Considering the state of dysthymia and feeling depressed as one end of a spectrum and a fulfilling, content "happy life" as the other, the sole determining metric is the degree of experiencing self-efficacy.

The experience of self-efficacy is witnessing your willing satisfy your desires and needs through your own working. And self-efficacy is a basic, most important human need, completely independent of grand ideological or intellectual nesting. You may experience it when putting on your pants, going for a run, or building a house; a successful hunt and finding shelter; you may or may not experience it through work. Doing something you deeply don't care about, lacking intrinsic motivation, luck and wealth alone do not grant you the experience of self-efficacy. It's not abstract power, but concrete evidence of you qualitatively changing your world for the better.

Seeking to increase this metric is not a basis for ethics, but guidance for finding lasting satisfaction in life, even under adversarial circumstances. Nihilism, or defeatism is learned helplessness, or depression made religion.