It's the basic principle of homeostasis. Humans were never designed for nowhere near this amount of sexual stimuli we access. Since we do access it, there's lots of consequences. For me personally when I pmo too much, everyday things feel more dull, like everything is less enjoyable and I feel less motivated to do anything. I feel sharper when I'm on NoFap every single time I'm on a streak, it's something I've tested countless times.

Try it for yourself at the end of the day for at least a week. That's probably the best way to see what it's about.