In theatre, you start with a text written by someone else. Your character says things and other characters reply. Problem is: you have no clue what they mean, or what their inner motivations are, when reading from the script. You have to go beyond the words and seek the true goals of your character. And test it on stage over and over until you find the right goals, the right inner motivation, that will _make_ your character say the words they say and do the things they do.
In method acting, we call that their “super-objectives”.
The situation is the same when designing. We are told what the users want, we may have access to information from a survey, or even to the transcripts of interviews. But that only tells us what people say, not their true motivation. A tool they say they want to use, and even a task they say they want to perform, is not a motivation.
For instance, filling one’s timesheet has never been an inner goal (really, does completing a timesheet fill you with joy and fulfillment?).
Note that I said “guess”, because you can’t just deduce what they truly are. That is why you have to test them. Put them on trial. Prototype them as early as possible and confront them to the reality, the truth, of the stage.