Stop hiding/putting/sticking your head in the sand!
hide/stick/put/bury (one's) head in the sand
: to refuse to deal with unpleasant realities, possible dangers, etc. by pretending they do not exist.
The term comes from the practice of ostriches, who spend a good deal of time burrowing headfirst in the sand. Most of the time they are eating, for these large, flightless birds consume sand and gravel, which are used in their gizzards to help digest food. However, it was long thought that they put their heads down in the mistaken belief that they then cannot be seen, and from the early seventeenth century on this mythical self-delusion was transferred to human beings who are avoiding unpleasantness.
"Stop sticking your head in the sand, Tim. Don’t pretend that everything’s all right."
"Lou, you can't hide your head in the sand about your health—please, make an appointment with your doctor and get that rash checked out!"
A: "How has Peter been handling the breakup?" B: "Oh, just putting his head in the sand and ignoring his feelings."
"Stop burying your head in the sand. Look at the statistics on smoking and cancer."