When evolution selects its agents, it does so at a cost. It makes demands in exchange for singularity, and you may be asked to do something against your very nature. Suddenly the change in your life that should have been wonderful comes as a betrayal. It may seem cruel, but the goal is nothing short of self-preservation, survival.
This force, evolution, is not sentimental. Like the earth itself, it knows only the hard facts of life's struggle with death. All you can do is hope and trust that when you've served its needs faithfully, there may still remain some glimmer of the life you once knew.