For years, I felt guilty (or was made to feel guilty) for giving an accurate/realistic estimate. Mostly at startups, where you feel, everyday, that the company is at risk of failing.
It's better to give a range of estimates - best case to worst case. Although managers may only hear the best case.
Sure, but especially when I'm made to feel guilty, my answer is always: the estimate I give does not influence how quickly the work is going to get done, so feel free to tell yourself that it will take half the time if that makes you feel better. I want to make it as explicit as possible that, if a manager only hears the best case, that's of their own volition.
It's better to give a range of estimates - best case to worst case. Although managers may only hear the best case.