Why is it so god damn hard?

I believe I’ve done some difficult things in my life—losing weight, serving in the military, running 50 km non-stop for six hours, climbing a mountain, and quitting drugs. But nothing even comes close to the difficulty I’m having with NoFap. And I can’t wrap my head around why it’s so hard. All I know is that there’s something deeply animalistic inside me, screaming with urges with all its might.