Profit is "Sales minus Expenses." Cash Flow is "Money In minus Money Out." They are not the same timing.
If you spend $50,000 on materials in January, but your client doesn't pay the $80,000 invoice until April, you have a $30,000 profit, but you might go bankrupt in February because you have $0 cash.
The Fix: Invoice Terms
Shorten your payment terms. Use "Net 15" instead of "Net 30." Ask for 50% upfront deposits on all large Quotes.