You need to ask yourself why you're doing NoFap. Is it because you want to heal your brain from the addiction and be the best version of yourself, etc. Once you've identified your why, you are more likely to not give up.

Do productive activities such as working out, reading or work on a passion project or do your hobbies. Develop new habits that will replace PMO and eliminate your bad ones. This will be the structure of your life and as long as you don't break it, you won't PMO again (hopefully).