The secret, as I posted elsewhere, is that self-control is something you need to practice, like going to the gym for your amygdala. Every time your resolve wavers, resisting temptations gets harder. Every time you resist, the next time gets easier.
This is what accounts for the stark differences in outlook. If you've practiced this, it feels easy, and it can be difficult to even relate to how others struggle. If you don't, it feels impossible, and it can be difficult to relate to how others find it so easy.
It can be a surprisingly quick process. If you have some impossibly tempting snack you're struggling to resist, if you just grin and willpower your way through it a couple of times, rough as they may be, it takes less willpower each time. By the 5th or 6th time you've done this, it's maybe still effortful, but already noticeably easier. By the 20th time, you may not even feel the temptation at all.
... depending on what's got you hooked, obviously. Substance addictions may linger for a longer time, but the principle is the same. Even if you still crave cigarettes two months after you've quit, it's nowhere near as bad as it was 5 days in.
It's not without reason almost every culture has had rituals of fasting or abstinence. It turns out this is a pretty good thing to practice every once in a while, even if you don't have to become a desert ascetic or go full Jocko Willink in the process.