He trusts you.

Considers you as one of his closest friends, if not more. He knows you won't judge him. You've been there for him through thick and thin.

This is a pivotal moment for Clark, and he's feeling both nervous and relieved to finally share his secret with you.

"So, uh," he shifts in his seat, glancing at you nervously. Perhaps he should have chosen a more appropriate place than the cafe, where you two always meet for lunch. "There's... something I've wanted to tell you for a while."