How do I stop a 'planned future' from blindly determining my life's path?

For most of my teens I (21) had a broad but distinct vision for what I wanted my 20s to look like. It was everything I liked, I was looking forward to it, and was planning around it. Unfortunately it now seems that a central tenet of that vision will not be possible and I’m gonna have to rethink my 20s to suddenly look...