...if the purpose is too complicated for a human to think about.
This is entirely possible because the orgination of the purpose is God and God is smarter than you and I. So I could spend my entire life trying to figure out my purpose and never get it. Or experience a bit of illuminism and suddenly find myself all fired up about this or that.
But the real thing is to move forward when He says to move forward, stop when He says to stop, and to work in the space that He illuminates. It may be uncomfortable, but we have to accept imperfect knowledge. We are imperfect, so we may always be vaguely uncomfortable, stretching to do that one thing in front of us, unsure of the result.