Cake
A woman in a diet club was lamenting that she had gained weight. She'd made her family's favourite cake over the weekend, she reported, and they'd eaten half of it at dinner.
The next day, she said, she kept staring at the other half, until finally she cut a thin slice for herself.
One slice led to another, and soon the whole cake was gone.
The woman went on to tell us how upset she was with her lack of willpower, and how she knew her husband would be disappointed.
Everyone commiserated; until someone asked what her husband said when he found out.
She smiled, "He never found out. I made another cake and ate half!"