I'm sad to learn that Eugene Gendlin died on 1 May 2017.

He 'invented' and popularized the Focusing method, one of the most basic protocols of how to change yourself (in the relative/morality area). Tons of later developed methods are based on this.
He wasn't only a psychologist, but also a philosopher (creating the philosophical underpinnings describing the change that happens in the Focusing process), and it shows in the clarity and precisions of his writings.