we assumed what we were building was right
The One Mistake All Product Teams Make
David Cancel

It is safe to keep building heads down and think you are making progress. That is why I literally keep Josh Elman’s quote “Help your team (and company) ship the right product to your users” printed out on my wall. Article: https://medium.com/@joshelman/a-product-managers-job-63c09a43d0ec#.ncc38b8oa