How do you come to grips with the idea that you won't achieve something you really wanted?

I’m sure we’ve all had these times in our lives. We finally realize it’s not going to happen. It could be a pretty big deal, such as realizing you’re not going to have the relationship you wanted. Or maybe realizing you are going to achieve a life long goal.

For example, there was a time when I thought I’d never have a child. I really wanted the opportunity to be a father, and when I found out I was infertile, the bottom kind of dropped out of my world. Fortunately, technology changed, and we never gave up, and we were able to achieve this goal.

How do you deal with your disappointment? How do you deal with the loss of self-esteem? How do you turn yourself around so you can enjoy what you do have?