It's Okay to Cry

"...Mari?"

Her knees buckled, and he caught her as she slid to the ground. Her head lowered, and he realized she was trembling. "...can't. I can't let myself be akumatized."

Chat's heart shattered into a million pieces.

Or: Marinette feels the burden of not letting her negative emotions show, since Ladybug cannot let herself be akumatized, no matter what. A cat is there to let her vent.