Idiom
have blinders on
to not be able to recognize or accept what is happening around you.I don't know why I thought he was innocent — I guess I had blinders on.
Usage notes: sometimes used in the form put blinders on - to refuse to accept something:
They put blinders on because they found it easier to ignore her behavior than to do something about it.
Etymology: based on the literal meaning of blinders (= pieces of material attached next to a horse's eyes to keep it from seeing anything on either side)