You seem to be spending an inordinate amount of time on what you don't want and what you're worried about. That is where the core of the issue lies for you. Instead of focusing on that you need to switch and focus on how much you like what you do and what you like about it.

Focus on the age group that you want to work with and how much you enjoy working with them and how much you enjoy that job itself. And then spend some time imagining or feeling yourself working with that group that you want to work with. Do it right before sleep. Don't fall asleep until you give yourself some time to imagine or feel it before you doze off.

And do something different where any time you find yourself worrying about getting what you don't want stop yourself from doing that. Pivot onto imagining what you do want. Go for a scenario where instead of what you don't want you're doing what you do want. That right there will begin to help you get out of the worry recycle.