Leading up to the end of a relationship, did you ignore red flags, or really never see them?

Inspired by another recent question I won’t link to. Those of you who have found yourself in really bad relationships, did you see red flags early on? Did you rationalize them, ignore them, hope they would go away, blame yourself?

Or did you really never see the bad stuff coming? Just all of a sudden one day, you were with someone you didn’t recognize?