Self-will = a plan devised by my ego. Get get get.
Why does self-will fail?
Plans require competence.
Most people are incompetent most of the time.
Even if you're competent, others have plans, too.
So there's collision.
Reliance on future outcomes creates distress.
Fear. Anxiety. Frustration. Anger. Resentment.
Even getting does not produce happiness.
Getting produces anxiety of losing.
Plus disappointment, despair, and depression.
Depression is excellent.
It is a sign that the plan has failed.
And that there is no hope that the plan will ever succeed.
It is only the depressed who surrender truly.