Hesitation to advertise one's own positive characteristcs. It seems to stem from the popular misconception that it is bad to be better than other people. I have never understood it. If someone is good at something, why should they conceal it from those around them, when it might be used to improve the world? Shouldn't we encourage and celebrate individuals who are talented instead of forcing them to act normal out of some twisted desire to not feel inferior?
Anyway, never hide what you're capable of, because it doesn't help anyone, especially not you.