I agree that you have to grieve the expectations or ideas. I do not agree that you have to welcome the changes.

Think about other significant losses. Mourning is all about learning to cope with something significant that we do not welcome, such as a death. It is not about coming to welcome the death.

Here there was a death of sorts, the death of your expectations or ideas. I am very sorry for your loss. In mourning this loss, you can in time come to ease the pain, integrate the loss into your life, and build meaning from it.