When somebody, at work, asks if you can do something, pause for a moment before saying 'NO.'
Your first thought may be 'that's impossible,' but upon reflection you can probably figure out how to pull it off.
Indeed, there is a very good chance that what you are being asked to do is not what is really needed, anyway.
Think about it.
We usually evaluate what we can contribute to a situation by imagining that there is someone else who really has the required expertise -- and then we interpret our feelings of uncertainty as proof that we are inadequate compared to this all-knowing other (who, by the way, is going through the exact same drill with someone else.)
In reality, our uncertainty (and the humility that, hopefully, accompanies it), are the essential elements of what we really bring to the table -- a curiosity about 'the situation' -- and an open mindset that helps us listen to multiple points of view without being ruled by preconceived ideas and solutions."