Pretty low. A game may not peak my interest after buying but I don't necessarily consider it a bad game. It's often more than I'm busy with something else and add it to my "to play later" list.
Take a nice long break from gaming maybe?
How often do you look in your library, physical or digital, and think to yourself "I wish I hadn't bought that"?
Also, for physical copies, how often to do you sell your games thinking the same thing?