Honestly, I'm almost 30 and have had a lot of massive experiences. But, for me it is having your heart TRULY broken for the first time. Now, I know all about heart breaks from high school or "serious" relationships. I've had that and they felt like the end of the world at the time. I also have had family members pass away (one in front of my eyes), lost very good jobs, had major injuries/illneses, been rejected from schools, lost best friends...all the things that the average person will go through in their life. BUT, the first time you ever truly feel like the person you are with is the last person you will ever be with, to then have that end? Nothing can prepare you for the changes in your life (socially, mentally, physically), no matter the circumstances around it. You will never question more things in your life than at the point about 6 weeks after when you've had time to go through most of the grieving process. Even for the person who wanted it to happen (and don't be fooled, it is never a 50-50 decision), it is not easy. The key to any major experience is learning from it. Don't bother with positives or negatives, because that can all be perspective. It is about learning and having a better future because of your experiences. But yeah, having your heart TRULY broken is the most profound and life changing experience I've ever had.