Just one piece of cake?

Why is it that when I make a cake I can't have just one slice? I have zero willpower. Today I had four, count them, four pieces of chocolate cake with whipped vanilla frosting.  If the cake isn't there I don't worry about it, but if it's in the fridge I must consume a gross amount.  Now I'm bloated and disgusted.  The good news is that I have been trying to eat more fruits and veggies.  I recently found out that my husband, who is a little older than I am, has a better cholesterol and glucose reading than myself.  If that doesn't motivate me, what will?  Sometimes I can be competitive, but most of the time I sulk away in defeat.