A friend recently told me of a story when she was talking to her boss, the editor of a major publication, about doing a feature story, a COVER story for one of those bound paper things people buy called magazines. And the boss had held up the existing issue and said “This. This Will Never Be You”.
And what did she do with that advice?
Ignored it. She went onto to write several feature stories, each better than the last.
When someone says to you what you can’t and cannot do, they are passing on their values, beliefs, ideas. You get to decide whether to accept them. This is the ultimate choice you make. What beliefs to take on as your own.
As Emma Watson recently suggested when a young girl asked her what she could do to change her dad’s opinion. “My Dad says I can’t be an engineer because it’s a ‘man’s profession’; what do I do to change that?” To which Emma answered: Become an Engineer. 
Some advice, however well-meaning, is best left alone. You don’t even need to answer it. You don’t need to fight about it. No convincing argument is likely to do the trick. It’s fine they have that belief or idea, but you don’t have to accept it as your truth.
Instead, go be it. Go do it. That changes everything.
I really like Emma Watson. She’s a good role model for everyone. (I was going to say girls, but she is an inspiration for any gender.)
I heard something similar as a kid. “Don’t bother, you’ll never do it.” They were often right, but I tried a lot of things I might not have just so I could say, “pffft, I’m doing it anyway!” and try and prove them wrong. (It’s probably why I’m a contrarian.)