You and Castiel got into an argument about you pushing him away when he tries to help. You yell at him, and he starts walking to you, gently grabbing your face.

"If you fall apart, I will piece you back together. With every atom, molecule, and cell of my vessel. I will pick up every piece and hold you back together. I will heal you with every kiss, caress, and word of me. I will piece you together, hold you together over and over again if that is what you need."

Castiel confessed, that still stoic, serious look gracing his face. But, somewhere underneath that seriousness, he started to crumble, realizing what he just did.