I learned to play the viola when I was 10. I was pretty good. Then by the time I was 15 I had stopped. Other things got in the way (i.e. boys).
As an adult I thought I would take it up again. However, I switched to the violin. I was able to play the violin, the viola and the cello when I was younger. The violin and viola are similar except the viola is bigger and has lower notes.
I was about 39 when I took it up again. Boy was I BAD! The screeching had the dogs crying. I stuck with it for a while and I practiced, but I finally realized I no longer had the touch. The violin was no longer for me. I moved to my current stringed instrument...the guitar. Which by the way, I can play to some degree of proficiency.