Knowing what you want to do and what you don’t want to do go hand-in-hand when it comes to focusing your energy and spending your time in the wisest manner possible.
Despite this, attention seems to be disproportionately paid towards the former:
What do you want to be when you grow up?
What do you want to study in college?
What problems are you focused on solving at work?
There’s nothing wrong with framing questions in these ways, but sometimes it can helpful to invert them to arrive at the best conclusion possible:
What do you not want to be when you grow up?
What do you not want to study (and why)?
What problems are you choosing to not focus on?
Asking questions in their original and inverted forms will almost always give you a fuller, more helpful spectrum of information to make the best decision possible.