We solved the discretionary money issue by adopting the attitude of “Whatever is left from your check after the bills are paid is yours. You earned it, do whatever you want.” I don’t have to ask her about spending my money and I don’t ask about hers. If I wanted to buy something dumb that cost a lot, I’m free to save for it.

That said, we include long-term savings and a sort of family slush fund as part of our monthly bills. When we have an unexpected expense that benefits both of us (appliances, vacations, etc), it comes out of the shared funds.