Nowadays most people die of a sort of creeping common sense, and discover when it is too late that the only things one never regrets are one's mistakes.
You had once asked me if I was afraid of death. I said I was afraid of not living. I don't want to eke out my life like a resource in short supply. The only selfish life is a timid one. To hold back, to withdraw, to keep the best in reserve, both overvalues the self, and undervalues what the self is.
Questions are for the benefit of every student, not just the one raising his hand. If you don't have the starch to stand up in class and admit what you don't understand, then I don't have the time to explain it to you. If you don't have a policy against nonsense you can wind up with a dozen timid little rabbits lined up in the hall outside your office, all waiting to whisper the same imbecilic question in your ear.