Ask HN: I wish I knew before I launched my project

For 2021, I was planning to launch my first project to the public. I have gone through a long list of consideration points concerning technical and legal aspects but I still feel that I am missing some points (which I am not aware of because it‘s the first time). So I was curious if there are any people out there who had similar experiences which led to “I wish I knew at that time“ moments. Happy New Year everyone!