You can only go by what someone tells you.
Based upon what I've been told I've done it more than once.
Essentially it's rare (both people) agree to end a relationship.
Odds are the one who initiates the breakup has had a lot more time to process their decision. Sometimes what their ex may be calling a "broken heart" is actually the same (shock and hurt) they would have if they got fired from their job.
Rejection, shock, hurt and disappointment are often dramatically described as having a "broken heart". Habits & routines die hard.
In my own life when I reflect back on what I thought was a "broken heart" I can clearly see now that my heart wasn't "broken" because I really wasn't "in love".
I was a teenager with ranging hormones who thought he was "in love". The reality is I was just a full-time college student on campus living in a "cocoon' that didn't resemble the real world.
Much like those contestants who "fall in love" on the TV show "The Bachelor". Naturally it's easy to get caught up in someone when there is no "real world" stress/responsibilities tugging at you. You're staying on a tropical island, living in a mansion, going on romantic excursions, and not having to report to a job you hate, rely on each other to pay the rent, car note, utilities, help with household chores, and maybe even raise children.
Most of us trace our "broken heart" to our high school or college years when we led carefree lives with no responsibilities. We were wildly optimistic and super unrealistic about expectations of what life would be like.
When I was in Jr. High a 13 year old girl attempted to commit suicide because her 14 year old broke up with her to date the "new girl".
I've often wondered if when she was in her 20s, 30s, 40s, or had sons and daughters of her own would she truly believe a 13 year old girl should ever think life is not worth living? Should any 14 year old boy be held responsible for anyone's wellbeing? Absolutely not! However they too immature to know.
It's often our immaturity as teenagers that keeps us focused only on "NOW" which intensifies our heartaches.
A 17 year old can't envision being 25!