A little infidelity, a little cheating, is OK in a marriage -- or even protective of it -- if the sneaking is just about money. Note the emphasis on "little."
Take handbags. Some time back, The Wall Street Journal reported on a woman who kept a secret stash of cash so she could buy very expensive handbags without disclosing the prices to her husband.
"He just wouldn't understand," was her explanation. And he probably wouldn't have.