There is a massive difference between 'Pain' and 'Disinterest'.

Lets say you are super passionate about making the next big programming language. The task is huge, its monstrous. But you go about it eventually, meanwhile you stretching beyond means. You stay up awake whole nights, you are working weekends, you've stopped seeing your friends. All that 18 hr/day work is causing you immense tiredness, there is reasonable amount of failure you are seeing every day. All that failure and way things are going is humbling you down. Now despite there is pain here, you are still carrying on. Because you go on and on, despite situation and find ways to just keep doing it; Until you eventually win. This is what is will power.

There is a second scenario. You come to office 9 AM every day sharp. There is build failure you need to look into, which is some trivial ftp call timing out. You have nothing serious or challenging. All your innovations and extra efforts are treated by your immediate superiors as threat-to-their-positions and crushed ASAP. In fact all you do is fix builds, fix trivial bugs and add an occasional feature. Your time goes in hearing dis interesting stories of what totally irrelevant issues your colleagues are upon during stand ups, your afternoons are full of filling up boring time sheets and agile management software. You are doing this only because you want a health insurance, some assurance no one will fire you ASAP and some comfort pillow. You are just seasoned to do this routine, because of some fear of failure.

While the first situation has tremendous pain associated with it, you are putting up effort in situations where others can't.

The second one is clearly the craving for safety, fear of failure and total non willingness to change unless forced to. This is some what opposite of Will power, because if you had it- you would be doing something else.