Don't fall in love with the product, fall in love with the problem
Bryan Cantrill: Love your customers
At Oxide, we believe that the best companies—the most enduring ones—love their customers, and we have made this explicit in our mission.
I had a mentor years ago tell me, "don't fall in love with the product, fall in love with the problem" and that's really stuck with me years later. To build a successful product, you need a monopoly.
Ahem…
If you aren't fortunate enough to have a monopoly, you need to solve people's problems, and as a product or design person, you need to be obsessed with advocating for those users and solving their problems. You can consider business needs as well, of course, but if you ever lose focus on being the advocate for your customers, you're down a bad road.