Will Power vs Why Power

I recently wrote about Willpower. On why it is scarce and how we should try to spend it on things that matter. If that's the case, can we do anything we need with willpower? 

In my personal opinion- it's a NO. The key to doing anything consistently or rather doing anything boils down to a strong WHY. On reflection, I have never continued doing something where I didn't have a strong WHY (good or bad). 

At times when I have continued doing things out of sheer willpower, I have been either been burnt out or just lost steam along the way. So I started asking WHY before taking up anything new.

I'm okay to give up on projects if the WHY is not relevant to me anymore.