All too often, they younger your friends are, the harder it is for them to deal with your chronic illness. Young adults are usually very healty and active and seeing someone their own age sick and disabled is more scarey for them that it is for people with more life experience. They also tend to be the 3yo of the adult world -- running around madly, doing everything they can because, OMG, they're independent and the world is so big and fun.
Community college is often a good place to find people who understand life's difficulties, especially if you take classes late in the day or in the evening. Those times tend to have more older students. Also, community colleges often have good disability resource programs that can help you deal with your disability while in college, and connect you with people who are mentally more adapted to people with more limitations than your average young adult. Your local community college may be different, of course.
If you try university, make sure you connect with the disabilities office.
There are a lot of fair weather friends out there.

You can't do much more than do things you enjoy and try to hook up with mature people, whatever their age.