Has he ever realized that what he feared most has actually made him stronger?

He saw death blow his brother's away so many times, until it was time to face the real thing. He said once, he had to become like Dean to survive it all. He has. He's the cold-blooded slaughterer of monsters, the heartless avenger looking for a purpose to this nonsense? Dean was his Achilles' heal, no denying that. But he'd surrender to evil to bring him back. He wasn't simply ready yet, not even after all these ironically-repeated deaths.

Stronger, but still so fragile without Dean.