Consider an addict having a relapse. Her promise was not to drink. Was she unable or unwilling to keep her promise?
Consider someone with crippling depression. Are they unable to feel better, or just unwilling?
Consider someone sitting at home eating Bugles and staring at his navel. Do I lack the will to go to the gym, or am I actually unable to?
These are the same question, and there’s no “true” answer. But there is an empowering answer. By holding this answer, I have a great deal more say in how things go in and around my life, and people I couldn’t relate to before, make a lot more sense.