For most of us, payday is a relief. For the typical small business owner, it’s a nail-biter.

In her latest book, “Fintech, Small Business & the American Dream,” Karen G. Mills, senior fellow at Harvard Business School, shares one entrepreneur’s payday struggles. In chapter eight, Mills profiles a brewery owner who isn’t sure whether she can afford to pay both her team and her vendors. Until she strings together data from dozens of apps and accounts, she doesn’t know whether her business will be in the black or red that month.

If you think Mills might have cherry-picked her example, consider that 63 percent of small business owners surveyed by online lender Kabbage say they’re regularly stressed about cash flow. The problem is so persistent that more than half of them had even gone multiple months without paying themselves.