Cash and accounting are often two different things. Receiving cash in is not necessarily the same as generating revenue, and having a good level of revenue is not necessarily the same as receiving cash.
In accounting, there are non-cash transactions, and as your organisation gets bigger, the non-cash transactions can be greater and greater.
Some areas, like expenses, can be easily plotted. They are regular and mostly known about.
Some areas, like income, may not be so easy to plot (especially if you work on projects or have intermittent income).
Timing can be a huge influencer on cashflow! When plotting your income and expenses, look at EXACTLY when you expect the transactions to happen. Whilst you may pay your suppliers regularly, your clients may not pay you when you expect them to. Perhaps build in some buffer time - if a client pays you a month later than you expect, what effect will that have?
Find useful info to help you understand more about your business, its accounts and finances.