Most Helpful Girl
Because it teaches you that you can survive hardships, it teaches you lessons in what to take from the relationship, you learn more about yourself and what you like/dislike. It's really how you choose to look at it. You can make it a miserable time, or you can choose to make it something positive. One attitude just makes you happy while the other sad. Your choice.
Most Helpful Guy
You come out of it with a better understanding of your own emotional pain tolerance and you know the sort of psychological abuse that you can withstand. I personally am not the same person by any means but I know my coping period, how I handle the stages of grief/hardship, and I feel like I can take it again if that's where life dumps me. I'm by no caliber happier or sadder than I was, but I look at things differently and I've recognized that it's not futile and it was honestly worth it for how happy she is and the peace I've made with it. But it varies for each person so I can't say the same applies to anyone else.