Does God Forsake You If Cancer Surgery Isn't 100% Successful?

Did God Forsake You If Cancer Surgery Isn’t 100% Successful?

Never will I leave you or forsake you. I suppose pretty much every Christians knows that line. Or something like it, depending on which translation you read. It’s from God. But do we know where it comes from? And of course, the ultimate questions related to that line – do we believe God will never forsake us and do we live like we believe it?