It takes an amount of cognitive load to do anything, and our reserves for this i.e. "willpower" is finite.
So why do we waste it on shallow endeavours?
To answer this question we must go deeper, or step back far enough to see the bigger issues at play for why we do this.
How we think of ourselves and what defines us as people, whether this was something we came up with ourselves or imposed on us by our parents, friends etc, we will inevitably steer the "ship" towards whatever these things are.
Once we correct for this definition i.e. by changing it to what we really want it to be, or get rid of it altogether, will we ever have a chance to get to where we really wanted to go.
Our "willpower" then, can be better utilised to gently manage us back on track or back to the task that's fully aligned with our chosen destiny. A rudder to steer us in our ocean of ambition.