This isn't really the place to talk about personal stuff like that, but the top 3 things you need to do are as follows:
1.cut that person out of your life. you dont need 'em, and that's final. it'll be better long-term.
2. fill up your free time with entertaining things to do. the less time you have with your thoughts, the less time you'll have thinking about 'em.
3. be with friends. the best distraction is having fun with people who understand you.
Btw Source for the pic pls?
Pretty sure this is the place as it's "general discussion,"… no need to be an ass.
(these tips are supposed to keep intrusive thoughts in check but i bet it can help you to forget ur ex too)