In The Lego Batman Movie, computer say this words to Batman:
Computer: You also have beautiful abs, sir.
Batman: That's my cross to bear.
Google says it is English Idiom, but meaning of it confusing in this sentence.
Ultimately it is a reference to the ancient practice of execution by crucifixion, where the person was attached to a large wooden cross and left to die, and specifically to the carrying of the cross by Jesus of Nazareth, who is central to Christianity.
A "cross to bear" has come to mean a hardship that one must endure.
When the "hardship" is not really a hardship at all, as here, the exaggeration is meant to be a joke of some kind. If the speaker is serious and does not believe he is exaggerating, then he is being portrayed as outrageously solipsistic, totally lacking in perspective.