Ever run into problem after problem that leaves you drained? I have and so has just about anyone who has had to figure something out on their own. Things would go so backward for me at times when I was first starting out on my own that my mentor would often say "stupid people have stupid problems" in response to my petty complaints. It took years and seeing another person struggle to understand what he meant by that phase. This is my estimate of it.
Joey* was a good friend of mine from my youth. He was very fun to be around, but he always was stuck on some personal issue that just never seemed to go his way. He always was in some sort of difficulty with his boss, friends, family, etc. After he had been evicted during the recession I offered him a place to stay until he got back on his feet. Initially, Joey worked for a construction company when he moved in, after he was let go he explained that it was out of his hands as the company had been downsizing on account of the shrinking economy. Feeling sympathy for Joey I let his share of the rent slide, after all, he was just couch surfing anyway. I soon found out that he wasn't doing just that, he was running up the water bill, eating everything he could find in the kitchen, and trashing my things while I was at work during the day (r.i.p my Pottery Barn towels).
Joey did find another job within a few weeks, this time as a car detailer for a used car dealership. When he had collected a number of paychecks I told him that if he were to continue living with me he would have to start paying for the things he used in the apartment. Agreeing Joey handed me some cash for what he felt he owed me and then went about his business. Soon there were massive packages at the door waiting for Joey. These packages were the least valuable things I could think of. Items like unofficial James Bond logo kitchenware and boxes and boxes of used car parts. Still, I thought that Joey was an adult and as long as he paid the bills it was none of my concern if he blew his paycheck on worthless clutter.
By the end of the month that I finally understood my mentor's rude motto, "stupid people have stupid problems." Joey had been skipping work and had been fired, only he didn't stop buying expensive bulk items or look for more work either. Joey came to me the night before rent was due, crying that he could not pay for anything. I told him I would help him and he could return the things he bought to offset his lost income. Joey refused, he said he needed that surfboard that he was totally going to learn to use one day and he couldn't live without that box of beaded car seat covers for a car he was really thinking about buying. According to Joey, it wasn't his fault that the economy had crashed, he was a victim of circumstance in his mind. My sympathy had been tested too long by that point though.
Joey's problem wasn't socio-economic conditions. It was an otherwise competent adult making terrible decisions with the expectation that others would always go behind him like a subservient mother to undo his personal mistakes. For as much as I wanted to help Joey, my pity for him had become the equivalent of tying bricks to myself and jumping in a lake. Treading water or in actuality maintaining our friendship would eventually cause me to drown, financially anyway. Joey had become my stupid person who was causing me stupid problems. Allowing him to run all over me with his every sob story was taking time away from my life and my happiness. Instead, I was picking up after him and using my money to cover for his impulse buying. Had I let this carry on for an extended period of time I would have been an idiot's keeper and lost myself to the task of it.
Ultimately the "Joeys" of the world are life suckers that will be as nice as they can be to keep you hanging on to be of use to them. Obviously, the "stupid people have stupid problems" theory can be applied to a multitude of situations, Joey being one of them. It could be that flipping off a cop who pulled you over for a broken taillight causes you bigger problems than you already had, making you the stupid person at that moment. Always be ready to double-check your reasoning in case the "stupid" person is in fact you, be sure to not incorrectly label another person as the "stupid one" in your situation. "Stupid people have stupid problems" is a warning, not to let judgment or reasoning errors produce more trouble than you need for yourself, whether you are the stupid person or you are allowing a stupid person to cause those problems for you.
*names changed to protect privacy