One person’s hallmark of mental strength might involve taking a little more time off to relax. Another person’s evidence of bigger mental muscles might involve pushing themselves to do more even though they don’t feel like it.
Our behavior doesn’t always reveal the battle we’re fighting inside our own minds. So it’s important to remember that your actions are only part of the process. Mental strength also involves the way you think and the way you feel.
Fortunately, there is a strategy that can help you discover whether you’re growing mentally stronger, even if your behavior doesn’t change right away. 
This one question can help you measure your mental strength every day.