Ineffable Ontological Detanglement .: Introspective Assistance & Mental Analysis Manual
You need to think. Maybe you are an imposter. Maybe it's something else, maybe there's one layer of "I am an imposter" beneath where you think it is. The thing you feel may be false about yourself may actually be true about yourself, but underneath that you feel your entire ego construction is false. Somewhere along the lines you built yourself something false, and now you question all of it. You either became something you knew you never really were or you're lying to yourself over what you are. It does not mean the thing you are looking at is false, it does not mean all of it is false, but somewhere deep something is false.
A lack of confidence is likely due to the fact that at some point you felt yourself overreaching into something and claiming a false confidence, now you feel you can't do the thing you are doing and everybody is going to find out. Well, maybe your false ego construction drove itself into something it cannot achieve and you are correct, you are an imposter.
Honest uncertainty over a task being manageable by yourself does not make you an imposter, but, generally, tell the people you are uncertain of your abilities. Not telling people of your uncertainty means... Deep down... Maybe you are an imposter. It doesn't mean you can't do the thing that is triggering your imposter syndrome. However maybe you should let somebody who knows what they're doing handle this thing, imposter. If you seem to be the best man for the job but you're still uncertain people are generally probably better off knowing. Also, if they're not as surprised by your failure you'll have less cognitive load as you attempt to complete the task and you're more likely to pull it off. Succeed or fail there's no way you will be revealed as an imposter.
If you're thinking "But if I tell the people I'm not sure of myself, they would become just as frightened as I am." I'm afraid you are now being too kind and gentle, keeping people in a false reality. Obviously highly complicated. Sometimes there is no other option, most of the time there is always the option of honesty. If you find yourself in a situation where people's reliance on the solution you offer could trigger a panic if they knew your feelings and so you cannot reveal your feelings... You may be an imposter. Or maybe you're just a world leader.
Ego invested psychology likes to keep you in your own little world, there's no such thing as an imposter. WELL. THEN. What is this thing I'm feeling? Not a thing the psychiatrist knows what you're feeling so it couldn't possibly be what you're feeling. Either in the sense of literal ignorance or in the sense of perfect internal cover up.