What does it mean to be strong?

What does it mean to be strong? Is it putting that smile independent
of how broken are you inside? Or is it
laughing when the only thing you
want to do is cry? People keep telling me - "You're strong", "You've got this", and "You can do this". From an early age, I've proven that to be the case. I've done
sports, school competitions, and I could achieve and fix anything I wanted.
I left home, family, and friends and moved abroad in my early twenties. Everyone was applauding - Look at her, she managed on her own. She did it. She's so young and managed on her own in a new country.
Indeed I did. Not only that, but I also enjoyed it. I found a home in a country very distinct from mine. I dare to say I got an amazing career in a short time as well. I've been my mom's greatest support when my dad passed away. And on top of all thing I have on my plate, I somehow manage to think of everyone & everything (for example - I organized flowers for my grandmother's birthday today although we're in different countries and she's in a small town where flowers delivery is not an option).
Despite all that validation & facts at times like those, I feel so weak. I know what's to be done, I know the conscious or unconscious methods my spouse uses to manipulate me, I recognize when my thoughts & feelings are triggered by the circumstances
and not my beliefs and when they "work against me". But yet I feel hopeless & weak. I find it difficult to see my happy ending. On days I feel like I'm drowning. The simple "How are you?" brings me to tears. And then my overthinking self starts questioning - where's that strong woman everyone sees? How do I find her more often? Moreover, how do I find her when I need her?
It's very easy to be strong when you have a clear mind and you're not overwhelmed by situations and people around you. But very tricky to flow above the water and find strength when the only thing you want to do is close in yourself. So am I really strong?