Motivation and expectation of success create a feedback loop:

Procrastination may be a delaying tactic to avoid wasting energy here and now, even if you think you might work harder later on.

Our conscious mind may be functioning more by making reasonable-sounding explanations for its behavior rather than actually making decisions.

Traditional approaches often focus on human will alone. But, our minds are complicated things, with many conscious and unconscious control mechanisms.

Inaction is the biggest cause of our failures and our miseries. If we could consistently do the things we know we should do, we would be more successful, and our lives would be better. Yet we struggle to take action.

Some possible but weak reasons why action is hard:

Our nature may be to view the cost-benefits of taking actions and be willing to retreat to conformity instead of getting punished.