Hey Buddy.
I can understand your emotional state and trauma through which you are going through right now. It really feels bad when you saw a partner (even casual or short term) moving away from you to someone. I went through such trauma and it is painful.
I want to share you few things to cope up with it:
1. Acceptance is the only way to get out of depression or anger or aggression emotional state which just came after bad news or rejection. A few quotes images I want to share for you to understand.
2. Don’t judge yourself
3. Take a deep breath and laid out a new plan to get out of boredom. Plan to make a new partner.
Hope it will guide you. Be happy Buddy, cheer up.