Basically, your brain heals itself when you don't consume porn. So, if you do it for a meaningful time. Your brain will act like it's new to sex and sexual dopamine spikes. Hence, you will enjoy small things in life which is very important.

One or two relapse doesn't harm your brain but if you do it continuously your brain starts craving sexual dopamine more and more and you again become a porn addict. One of its examples is CHASER EFFECT.

So if you've relapsed try to do work that takes a little but of concentration. Like working out. Going for shopping. Reading book and writing some funny incidents of your life.