Kill your darlings. Fall in love with the problem, not the solution.
Article: Kill Your Darlings
Kill your darlings usually means a writer decides to remove unnecessary sentences, paragraphs, or characters in their work. They get rid of the elements they have worked hard to create but must be removed for the sake of the overall story. What we set out to write is not always what we actually write. In these circumstances, we must have the courage to "kill the darlings" we have worked hard on.
This can be generalized to things like building software, making products, or even just solving problems. What we set out to do is not always what we do. Sometimes, what we set out to do is even not what we should do. When we fall in love with the things we build, it's hard to see the flaws. The more time we worked on our solution, the harder it became for us to change our minds when other people challenge our solutions.
Therefore, we should fall in love with the problem we aim to solve in the first place, instead of the solution we have spent time on time to build.