You find out something about your loved one and you can't bear to tell him/her the truth, feeling it would shatter that person's innocence and sanity. So you tell a little white lie to make the blow less powerful and all is well.
Compare Daddy Had a Good Reason for Abandoning You
- Joe Dirt has Brandy telling Joe that his parents died at the Grand Canyon when he was a kid. However, his parents contact him and turn out to be alive and they reveal that they left him behind on purpose. He finally breaks and as he's on the verge of suicide, Brandy comes in and tells him the truth: that she managed to find his parents, then lied when she found out how horrible they were.
- In the King of the Hill episode "Life: A Loser's Manual", it's revealed that Hank and Peggy lied to Luanne about her father working on an oil rig so they can spare her feelings. Really, he has a nasty drug addiction and was in jail all this time.
- In the Futurama episode "Leela's Homeworld", it's revealed that Leela is a sewer mutant that was abandoned on the surface so she would be spared the shame of being a mutant and pass off as an alien.