How do you deal with being cheated on and dumped?

So I had this pretty long relathionship. I just found out that the person had another relationship with somebody else for couple of months now. And that he likes that other person better and does not want to continue a relationship with me. Unfortunately I have to face him couple of days a week since we have work connections. I just am not sure how to handle it. I just feel so stupid since I felt that we had great connection and I must say I was pretty much very in love. Tweet