What you don't know won't hurt you
What you don't know won't hurt you.and What you don't know can't hurt you.
Prov. If you do not know about a problem or a misdeed, you will not be able to make yourself unhappy by worrying about it. (Often used to justify not telling someone about a problem or misdeed.) Ellen: What a beautiful diamond necklace! Thank you! But how on earth did you get the money to pay for it? Fred: What you don't know won't hurt you.