Here are some quotes about strength that can be used as tattoos:

- "A smooth sea never made a skilled sailor." - Franklin D. Roosevelt
- "Strength does not come from physical capacity. It comes from an indomitable will." - Mahatma Gandhi
- "The world breaks everyone, and afterward, some are strong at the broken places." - Ernest Hemingway
- "I am not afraid of storms for I am learning how to sail my ship." - Louisa May Alcott
- "The only way out is through." - Robert Frost
- "Fall seven times, stand up eight." - Japanese Proverb

I hope these help! Let me know if you need anything else.