I’m looking for a book on helping you accept change you cannot control.

I felt like I was in the best spot of my life. I was thriving and excited about the future. And then my best friend who I was doing it all with got a boyfriend. While I'm supportive, it's been extremely painful to realize how it is changing my entire life when I don't want it to change. It may sound extreme but you must understand our lives were very closely intertwined and this affects everything. I now am trying to cope that the reality of my life changed very quickly. I'm uncertain about my future and I'm having a hard time accepting that everything is changing for me, because I didn't make the change. I could really use a book of advice.