This is separate from the idea of an emergency or rainy day fund, which should be an additional 3-6 months expenses in an easy-to-access account, like a linked savings account.
I realize that if you're currently living paycheck-to-paycheck this can seem daunting. Definitely check out the video lessons on the YNAB site, and think about buying the software. There's probably a way to implement it in Quicken, but I have no idea.
https://www.youneedabudget.com/support/training-and-educatio...