Acceptance is supposed to be a good thing - Grant me the serenity to accept the things I cannot change. Also compromise, as every couples therapist will tell you. But the cost was high - the damping of expectation, the dwindling of spirit, the resignation that comes to replace enthusiasm, the cynicism that supplants hope. The mouldering that goes unnoticed and unchecked.
In my life, there have been people that I was convinced would be around forever, and yet, somehow they managed to drift away after a couple of years. Likewise there have been people who have begun as casual acquaintances but become more important with each passing year.