I don't. I know that my mortgage/utilities/insurance/food bill is roughly X% of my take-home earnings. My savings are Y% of my earnings. X% + Y% is roughly ~9

I don't. I know that my mortgage/utilities/insurance/food bill is roughly X% of my take-home earnings. My savings are Y% of my earnings. X% + Y% is roughly ~90%. The other 10% is an everything fund that goes to my liquid checking account in the bank. So that bank account is growing very slightly. So the only thing required from me is to look at the bank account once a quarter or so, and make sure it's still roughly at the same level and there were no outlier expenses.