He's strong enough to admit when he's wrong.
It takes a person strong in character and secure in themselves to say "I was wrong" or "I'm sorry", and do it with sincerity. These days, those phrases are too often tossed around like meaningless cheese puffs, full of air and nothing else, just so the person who had to say it can go on about doing whatever they did to get there in the first place - just more sneakily or underhandedly.
If my husband says "I was wrong" or "I'm sorry" you can take it to the bank that he means it with all sincerity. He's not blowing smoke just to move on. He'll genuinely do whatever he can to make it right and ensure that thing doesn't happen again. He hates being wrong. He hates having to apologize or ask forgiveness. But he'll absolutely do it in a heartbeat if he's messed up somehow.
His willingness to humble himself keeps me humble too. I don't hold things over his head, and he doesn't hold things over mine. I've learned how to say I'm sorry from him. He's taught me that admitting wrong doesn't mean you're going to get bashed over the head for it, but it does allow you to move forward with a clear conscience.
I love my husband because he's taught me that being wrong, saying you were wrong, or saying you're sorry, doesn't mean you're bad, or weak. In fact, the ability to do so sincerely makes you the exact opposite. It makes you strong and good and trustworthy.