I guess you'd have to "start over" and you'd be slower, etc. than 3 years ago? And lots can happen in 3 years, especially if you were sick. My appendix burst 3 years ago and I'm totally different physically, asthma has developed and last Spring I was in training and the asthma flared and I haven't been back to the gym/personal trainer.

When I was in my mid-20s, back in the 1970s and lived in a large City I use to ride my 10 speed 9-10 miles to work. At first I couldn't pedal very long but then I got so I could pedal up steep hills instead of having to get off, etc., just like you remember with your running. When I occasionally drive one hill again, I remember and am amazed :-)

Life changes. I wouldn't do the exercise/running, etc. thing anymore if you don't enjoy it? If the anxiety is getting in the way, it's probably telling you something (including to drink plenty of liquids/water :-) Can you think of another sport/activity you'd like to try?