I recently discovered, which was difficult as an atheist, a huge body of work on this, under the topics "spirituality" and "philosophy". It makes so much sense now, but we've lost touch with it in our modern society. The idea of "what makes a successful human life" has been the hottest topic of written literature for all of history, it's just that we've lost a little touch it.

We can also measure people's height, yet we usually don't use it as a metric for success in life (you also don't see that many how to be tall posts).

The only difference is, the metrics I listed are all metrics of success in life (according to different viewpoints). The personal feeling of satisfaction is a metric from the viewpoint of an individualist. The impact on society is a metric from the viewpoint of a socialist (or possibly a historian). The number of offspring is reproductive success, which is all what counts from the viewpoint of an evolutionary biologist. (And of course I completely forgot to account for the viewpoint of a theologian.)

I am not sure these viewpoints are reconcilable.

As opposed to financial success.