+1 to Herc. I have my designated "savings" pulled from my pay automatically so I can't touch it. Also, savings and retirement are different. Retirement pay goes right to the IRA which is in a mutual fund, savings is cash for emergencies or planned large purchases which goes right to a money market account.
Retirement money does not get touched, ever. Ever.
Savings money gets used for unusual purchases, the new dining room set, new tires for the car, etc. Its nice to be able to buy the wife new tires when she needs them and pay cash, or to be able to walk into a furniture store and tell the salesman you don't care about their financing "deal" because you're paying cash. Just don't wipe out your savings doing that too often.
Also, because I've already put the money I want to save away, I don't feel bad burning through the rest of the paycheck each pay period. As if that wasn't already the only option when you add in the wife's access to the checkbook.