Bury/have your head in the sand
to refuse to think about unpleasant facts, although they will have an influence on your situation:
You’ve got to face facts here – you can’t just bury your head in the sand.
Do ostriches really bury their head in the sand?
As flightless birds, ostriches are unable to build nests in trees, so they lay their eggs in holes dug in the ground. To make sure that the eggs are evenly heated, they occasionally stick their heads into the nest to rotate the eggs, which makes it look like they’re trying to hide – hence the myth. An ostrich trying to hide from predators in this way wouldn’t last for long, and it wouldn’t be able to breathe, either!