Have you ever found out something about someone that you wish you could somehow un-know?

What are you supposed to do when it is something so disturbing that just imagining it makes you feel physically ill?

What do you do if it's something you simply cannot tell another soul,ever,because it could cause so much harm,not just to yourself but to other people as well?

And what if you are actually afraid of what you know?Like,even afraid that someone may even find out you know?

How do you possibly un-know something?