Unless it's their background, finance is the area most business owners find hardest to get their head around. The concept that took me longest was that profit and cash flow are not the same thing, and I learned it the hard way.
A lot of businesses bill in a way that makes this worse. Annual agreements, multi-year contracts, project deposits, anything where money arrives in lumps while the costs run every single month. On the P&L that revenue gets spread evenly across the year, so profitability looks steady and reasonable. The bank account tells a completely different story, and the two almost never get looked at with the same attention.
That gap is where owners get caught. If you're only looking at your profit line every month, you're only looking at a long term picture. If you only look at your bank account (and I've encountered this one more often), it could have a pile of cash in it right now that doesn't belong to you. Both lead to making decisions based on incomplete data.
If you have a bad month or quarter on the P&L, you have time to fix it. If you aren't paying attention and run out of cash, it's over. Payroll bounces. Your people aren't getting paid for the work they did. For you.
That's the weight a business owner carries around with them.
Look at your cash daily. Build a cash flow forecast and look at it weekly. If you see an issue, act on it. Even if you have financial staff, this is a key way to keep them accountable.
Working out which numbers actually matter in your business, and building the routine that keeps them in front of you, is a lot of what I do with owners.
Don't learn that lesson the way I did.