Gap problems? what should I do?

My dentist said I might need braces and they said it's a good idea but they said that my mussel on top of my gap is pushing my teeth a part and that is why I have a gap. I was wondering if I ever get braces and sometime maybe in like 2 years take them off um will my gap come back? My sister keeps saying that it will and it makes me sad. What should I do?