If humans would have the inherent characteristic to be alone and happy, perhaps the population would be a lot less and each one us would be occupying our own personal island. However, fortunately and unfortunately, we are highly evolved individuals, for whom to love and to be loved is a very basic necessity. Hence being in a relationship is an option which we do choose, to ensure our “Happily ever after life.”
But, with time only the relationship is left behind, with little or no happiness. This happens because we tend to forget what a relationship really means.