Have you ever noticed that one of the key tenets of the Stoics is essentially the Serenity Prayer?
The chief task in life is simply this: to identify and separate matters so that I can say clearly to myself which are externals not under my control, and which have to do with the choices I actually control. Where then do I look for good and evil? Not to uncontrollable externals, but within myself to the choices that are my own.
— Epictetus, Discourses, 2.5.4–5
God, grant me the serenity to accept the things I cannot change,
courage to change the things I can,
and wisdom to know the difference.
One need not be a theist to pray. That may be counterintuitive, but the exercise of putting thoughts into a concrete, coherent form has enormous value. There is an inner self that is always aware. And, just in case you’re wrong about theism, it can’t hurt.