By experiencing the sheer existential horror that Nietzsche and others spoke of and coming out of it knowing the only way out is through. There is nothing to lean on. You decide you start caring and it will happen.

For me, the metric is one of empathy: would I want someone else to suffer through what I just suffered through? No? Do I have any influence over that outcome?

The Serenity Prayer is very real to me. So is "be the change you want to see in the world"