Marriage Agreements may be useful. These agreements are ones that are made prior to cohabitation and usually at a time when the parties do not have an intention to separate in the future.
Sometimes the "milk is spilt"! A well-drafted Marriage Agreement would be akin to placing a pale under the table so as to collect the spilt milk instead of onto the floor in unpredictable ways.
Separation Agreements are made when a separation is occurring or has occurred. At this stage, litigation is a real threat and the parties are attempting to reach a settlement.