For me it's actually the other way around. I was scared of everything when I was younger and hated everything that was outside my comfort zone. And when I did try to leave my self-created bubble I was too worried of what other people might think about me bumbling around, so I always stopped halfway and never got around to anything meaningful. But when I got older I started giving less fucks about other people and got bolder and more open in the process, though it wasn't that much of a great leap and I was still hampered by those issues.
This year I started therapy and I realized that most if not all all of those anxiety and self-esteem issues resulted from untreated ADHD. I hope that with therapy and meds I'll make greater strides in becoming a more confident and well-adjusted dude, though I doubt I'm ever going to be an uninhibited social butterfly.
And yeah, even though some things got better with age, there is a lot of new stuff that worries me, now that I'm in my 30s, like responsibilities and particularly the fear of becoming feeble and lonely and not being able to care of myself when I'll grow old. But I guess that's what it means to be an adult...