Relationship is based on mutual understanding, commitment, respect on the feeling of each other and most importantly avoid hurting the ego of one you love. If you really care a person and build up your relationship with the base of above valuable aspects, there won't be anything which might let you go or make a fear in your mind of losing him or her.
People usually step in the relationship with high degree of excitement, commitment and understanding etc., as well in the beginning but the speed of their excitement turns slow when they take it granted that the opposite person will not be deserting them even if they do not show much concern towards this relationship.
They express their regret when the relationship ends or forced to end but by the time everything goes out of their hands. They vow to show their sincere effort again but they turn up empty handed and are considered to be losers.