Maturing Over Time
Children are expected to grow and learn over time, but few young adults see this as something that will happen to them. They tend to believe they are now grown up, and they will feel the same about the world in half a century from now. Understanding the maturing process of an adult does not happen until a person has decades behind them, and they choose to honestly look back at how they perceived the world in previous years.
Dating as a young adult is part of the process of finding a long term relationship. Not all dates will result in a relationship, and every young person should recognize this fact. Rejection may sting, but staying with the wrong partner will hurt worse. Some partners will break up because they see their significant other needs time to mature into an adult who can handle life's difficult situations. This does not always signify a lack of commitment or love, but it does show they believe they are restricting the other person's ability to mature.
Running into a former partner years later may give the couple a chance to reconnect. Both of them will have had the chance to mature, and they may be ready for a new relationship. Reconnecting might be difficult unless both understand why the relationship did not work the first time. The partner who was immature must acknowledge it, and their former love must accept they have matured enough to continue their former relationship.
There are few people who will wait years for another person to mature enough to have a successful relationship. They believe it is best to move on in life, and they continue searching for a mature partnership with someone else. Their search might not work because they are subconsciously waiting for their former partner to mature, and this is one of the main factors in being able to reconnect successfully.