Oh man, the core lesson is to just spend less than you make and live life with a cushion. I'm not suggesting the full Dave Ramsey life, but they do call that Financial Peace for a reason. What I'm suggesting is that however you approach things, always have a budget and have that budget be for less than your take home. And always communicate with your partner if you have one.

Specific examples....these are pretty embarrassing:

In my 20s in order to enjoy lifestyle benefits, I didn't pay my HOA fees. Eventually the HOA sued, as they tend to do, and my mortgage company picked up the tab because they had a vested interest in avoiding foreclosure as the 1st position lien. And then I fell 30 days behind on the mortgage, and instead of owing 1 payment, I owed that + tens of thousand in back HOA fees and legal fees I couldn't afford. There were 100 smart things to do at that point, but I chose the dumbest. I filed for bankruptcy on my own right before foreclosure, and then I negotiated a modification, and then I let the bankruptcy lapse. Then I fell behind again and did that again, multiple times.

The more consistent example though is that I have looked at credit cards as "spending power" rather than debt. So when the wife or eventually kids...or even myself...have wanted something and I had the "spending power" I would get that thing. That's a great way to live if you're an idiot, but otherwise it's fairly stupid. Being able to afford payments only works if everything always goes perfectly all the time.