You can control things, just not everything.

Y'all have never been to court ordered alcoholics anonymous meetings and it shows.

Reinhold Niebuhr wrote the first known version of the Serenity Prayer, and it's been through a few revisions just by popular word of mouth or even literal Hallmark greeting cards, but the version they say at AA meetings is:

God, grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference.

The basic principle can be decoupled from the religious origins and still be a useful approach to life. Learn not to stress about the things not in your control, while still taking control of the influence you do have.