I got my first grey hair at 21 and it really upset me - I guess it was the first sign I wasn't young anymore.

Since then there's been a whole load more signs I'm not young anymore so I'm used to it now - it's okay, getting old is a side effect of living.

If it's worry about aging behind your anxiety maybe you can work on that, maybe time to look at why you fear it and also balance your impression of aging with the positive things it has to offer - if that's what your fear is.