not for the life of (one)
Regardless of how hard one tries or how much is at stake. He had just met the woman yesterday, but he couldn't for the life of him remember her name. Not for the life of me have I been able to get the lid of this jar off. Can you try?
not for the life of me
No matter how hard I try. Used when one is totally unable to do something. I just met that woman yesterday, but not for the life of me can I remember her name. The lid of this jar won't come off for the life of me. Will you try?