You will never really be able to tell that you're an expert, if you are an expert. One of the reasons for this is because of the Dunning-Kruger effect in cognit

You will never really be able to tell that you're an expert, if you are an expert. One of the reasons for this is because of the Dunning-Kruger effect in cognitive psychology whereby "the highly skilled underrate their abilities, suffering from illusory inferiority". (http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect)