Consider who you are. Above all, a human being, carrying no greater power than your own reasoned choice, which oversees all other things, and is free from any other master.
Epictetus, from Discourses
Your hidden power is your ability to use reason and make choices, however limited or small.
What are the choices available to you, day after day? You might be surprised at how many there actually are. Are you taking advantage? Are you finding the positives?
The Daily Stoic: 366 Meditations on Wisdom, Perseverance, and the Art of Living
Background on Epictetus