How do I move on ?

So .. I’ve never posted on here but I felt like I wanted to get this off my chest . I was with my fiancé since I was 19 .. 13 years and a few months . 2 weeks ago he asked me for space , saying he wasn’t in love with me anymore and today we broke up . I am devastated. I still don’t comprehend how you can love someone for so long and then all of a sudden not anymore. I’m absolutely devastated and don’t know how I will every be able to move on . He was not my first but he was my only serious partner . I thought he has it for me ..... how do people do it ? How do they cope with this amount of pain and heart break ...