"Someone's opinion of you does NOT have to become your reality!" - Les Brown
Try this:
Assuming based on the fact that you are reading this right now, you know how to read. You've learned that skill. If you looked at a page in a novel BEFORE you had that skill versus AFTER you had the skill of literacy would you be able to look at the page the same once you knew how to read ever again? Probably not. Once you learn something you know it for life.
Now on a different note. How many people told you in life that you were no good at something like mathematics? I was told in grade 10 that I was terrible at math and I should continue in the general classes (rather than the advanced or applied). My entire life I was convinced that I could not do anything math related, thus leaving out some very viable career choices. I now deal with numbers all day every day in the stock market and I am excellent with math.
Why? What happened?
It's very simple, I told myself (and believed) that I was excellent at math. Once I accepted that I was great with numbers and started to learn how to calculate ROI (return on investment) or percentages or Fibonacci numbers I couldn't go back. Once I knew, I knew what I knew!
The point is two fold. You decide what you can and cannot do and then once you know, you know what you know forever.
Go ahead, tell yourself you CAN do something and then DO IT. Don't be intimidated. Remember that the masters all had to start somewhere and if you are worried you'll look silly trying something new I can guarantee that more people will be jealous of your tenacity than think you look silly.
Believe in yourself and remember the next time you don't know something, don't shoo it to the side; figure it out and empower yourself to KNOW.
REMEMBER don't negate something just because it scares the heck out of you. I bet you'd be great at it. Increasing your skill set can only help you to be more successful and a well rounded interesting individual.