Assuming you had a bippy to bet, it’s an important question to ask when designing an experience… You could certainly replace ‘bippy’ with something you value more than your bippy.
Experience design is a series of choices based on assumptions. Assuming a user has a certain problem is the only way to create solutions. But what if you look at a screen and ask yourself how confident you are about each of the features represented. How would each feature rank based on your level of confidence that it is both usable and desirable? Is that layout/widget/nav etc. the _right_ choice?
Becoming comfortable with a design by acclimating yourself to the level of risk represented is a natural progression. But every once in a while you face a firing squad that forces you to stand by a decision. Thar’s when it is time to ask yourself if you have enough information to look someone in the eyes and say ‘i am confident you should do this.’ or better yet, become your own firing squad.
If you can’t recommend something with a certain level of confidence, it is a great sign that you need to go back to users. Validating your assumptions can give you confidence to move forward without losing a bippy.