A very simple bad decision is to get into debt. And that is very expensive.
What people do is they pay the small loans first. Why? Because they enjoy making the number of loans smaller. But of course it is a very ineffective way to pay debt down.
The problem is that people basically dangle debt in front of us. And the cost for the poor of course is much higher than for the wealthy.
Not all debt is bad. From time to time we should get into debt when there's a good reason for that.