Many people begin dating in their teenage years, and that is often when two people may find they can agree on nothing. Their meetings are more like a projected war zone than a forum for asking and accepting a date. It can be hilarious to those around them, but it can also be damaging for the two people involved. While they may be at odds as teens, taking time to mature could see them in a lasting relationship with each other.
People often change their outlook on many things as they age. Experience is an excellent teacher, and what is learned after schooling is often more applicable to living in the real world. A person who has had a few years of working and trying to accomplish their own goals will often see the world with new eyes. If the person they fought with as a teenager is still around, it could be an opportunity to see if they have also matured.
The issues that younger people face are deeply important to them, and they are often interpreted in a more emotional way. Maturing properly helps people take the emotion out of the equation, and it often substitutes it with rationality. Two people willing to fight to the death as teens may see no reason at all to disagree once they have another decade of living under their belts. It can be a fascinating experience for family and friends to watch them reunite.
Not all former relationships of this nature will result in a couple getting together and creating their own stable relationship. They may meet at class reunions and be able to become friends. Each of them may end up with a spouse outside their class, or they might have dated and married someone else from school. The point is that these two people no longer need to exhibit the emotional angst of their teenage years, and they are able to get along with each other quite well as friends or former classmates.