One of the issues in any business is how big any customer is as a percentage of sales and that is normally one of the first questions a buyer of any business wants to know. While it's hard to turn down work and generally more efficient to deal with a few big accounts vs. many small accounts that is definitely a risk.
That said I wonder how many people getting hired by a company are fully aware of how large a companies clients are and what would happen to their job if any client left. At least in Patricks case he directly can keep his clients satisfied.
Plus losing a seventh or even half your income and then having a gap to look for new clients (you can ask existing clients for referrals) isn't anywhere near as risky as suddenly losing 100% of your income for reasons that can be fully beyond your control
But at least the risk is spread around. Having a fraction of your original income still coming in is far better than having absolutely no income coming in.
Can you explain this further?