If you have been on an income where you can resonably balance your spending and earning, then something happens, like you lose your job and cant keep up repayments, then its clear you havent done it on purpose.
(eg: £2k coming in, verses outgoings of £1k rent, £150 bills, £300 food & fuel, and say £200 credit card/ loan repayments).
You go max out your card with no evident means of repaying it when you used the credit, you may find yourself in a major crosswind, with no avionics and your arms strapped into your harness.
So if you know you cant repay the debts you take on, dont take them on.