feeling low after being cheated on,how to feel better?

[Jay]

I broke up with my now ex boyfriend because he was flirting and going on dates with this girl basically building a relationship with her behind my back,I made the mastake of keeping him on my social media and ended up seeing that he is in a relationship with the girl only after 2 weeks of being broken up it really saddened me cause i felt like that ment he never really loved me and I ended up cursing him out through an email,idk what i did wrong to deserve that the messed up part about it is that he was my actual bestfriend for some years and we was together for 2 years and on and off for another 2 years

[Doktor Evil]

Go out with some guy who is the complete opposite of him.