Take a look at stoicism. Not the pop modern version but the ancient roman and greek traditions of Seneca, Epictitus, and Marcus Aurelius.

Essentially letting go of controlling our lives in ways that cause suffering. Accepting that bad things can and do happen. Realising that life is temporary and we should focus ourselves on things in our power that make us a person of better character. Everything else is out of our control and should be accepted without judgement.

It's brought a lot of comfort to me over the years.