Authors:

He can who thinks he can, and he can't who thinks he can't.

Orison Swett Marden (2015). “An Iron Will, He Can Who Thinks He Can & Pushing To The Front (Wisdom & Empowerment Series): How to Achieve Self-Reliance Which Leads to Vigorous Self-Faith, Personal Growth & Success”, p.591, e-artnow
He can who thinks he can, and he can't who thinks he can't.