Two answers.
1) Keep a cash buffer that refills when you get your paycheck. Never worry about cash flow. Many of us keep a few months expenses liquid. See this post:
http://forum.mrmoneymustache.com/ask-a-mustachian/your-checking-account-balance/2) For this answer, I'm gonna post the opposite of the person above me:
It's a "save for yourself last" mentality. And that means you never need to worry about cash flow.
If you budget every dollar you earn to spend, you have nothing left. Cash flow is managed, but delicately, cause you could run out, since you're spending every dollar.
If you pay yourself first (take a big chunk out for savings) and then budget the rest, again, same issue, you delicately manage cash flow.
Those of us that don't have a budget don't need to worry about cash flow, because there's always enough.
Say the wife and I net 5k/mo together, and spend 2k/mo. Money comes in, we spend whatever we want, we flow money out to investments.. more comes in, we spend, etc. We're constantly overflowing with money, not having to worry about a budget because we LBYM.
And then we pay ourselves last. Once we buy whatever we want, we save the rest.
The key is to minimize what you want. But essentially you get your spending to as little as possible, and save the rest. Instead of saving a fixed X up front, you spend as little as you want, and save all the rest, at the end. And then you never have to worry about cash flow. Cash flow concerns are for people who budget.
(And people with irregular incomes, who either have to budget out of necessity, or keep a cash buffer).
If you budget, you worry about cash flow much more than those of us who budget, IMO.