What They Share
Both focused on what is within your control
The dichotomy of control is the core teaching for both. Despite their vastly different circumstances, both grounded their peace in the same principle.
Both saw philosophy as daily practice, not theory
Epictetus taught his students through exercises; Marcus practiced in his journal. Both treated philosophy as a toolkit for real life.
Both emphasized acceptance of fate and circumstance
The former slave and the emperor both taught that you must play whatever role life assigns you -- and play it well.