How can i be strong enough to not take back my ex?

Remind yourself that you deserve better. Don't let him hurt you again time after time. You deserve someone who would make you happy. When you think about accepting him back into your life, think about why you kicked him out of your life in the first place. It's not easy to let go of someone, but you have to for your own well being.

Never try to find happiness in the place where you lost it

you can start doing differences thinks like dance or painting or just do exercise in other words concentrate on other things