For me it's committment. 100% of what we both get goes into the joint account. I have a setup for work funds for expenses.
We don't charge unless we have the cash to pay for it when the statement comes. She grew up with barely enough money for expenses, I grew up in a family that borrowed every chance they had. I learned from my wife how to handle finances, we have benefited from the lessons.
The other half of the committment is a financial wizard. We were able to payoff our 30 year mortgage in 15 years. We've been able to pay cash for the last 3 cars we've bought.
I guess what works for each is what works.