What matters more when building a product: your opinion or users' opinion ?

I guess you always need to aim for balance. Even if you are your user and face the same problem, remember always about context and different perspectives, you should never consider only yours. In that matter is always important to identify your own biases and remember to user another lens to see the same problem, this could change a lot about how you see and understand things. But some gut felling is always good if you consider yourself an expert in your product area, otherwise could be really harmful. For example, I've already worked in the healthcare area, more precisely with digital prescriptions, it was really hard for me to take gut decisions. In general, aim for the balance. Get to know your users, fall in love with the problem (not the solutions), always avoid your 1st idea/solution, ask yourself if there are other ways to solve the problem and remember to use other people lens, not only yours! Good luck :D

A combination of both! But I think users' should always be a priority, especially if you are building a product that's going to be a business. Without their input, how will you sell? That said, you need to ensure you ask the right questions to actually get ahead and make progress. What do you think @realartemg?