elaborate
bagholding = entering into an investment which goes horribly wrong, and you are then down a significant %. Then, typically the psychological defense mechanism of unwarranted optimism/delusion takes place. "It'll go back up I'm in this for the long term...I'm right and the market is wrong, ect.,".
Bagholding is typically a choice as the investor opts not to sell for these reasons. In this case though these investors have to watch their holdings go down...30/40/50+% overnight without the ability to sell even if they wanted too.