1. You are unable to pay all your bills
If at the end of each month you have to prioritize and decide what bills to pay and which ones to default because you lack adequate cash, you should be worried.
Proper financial discipline advocates living within your means, where you can settle all your financial obligations when due.
Nevertheless, if you find yourself in this state, best solution is first to pay the bills protecting your home. For instance, you could start with the mortgage, then the car and eventually the credit card bills.