1. You can accumulate more and more debt, particularly credit card debt, over time, and eventually end up bankrupt. This process could take decades, however, particularly if you "cash out" your house using a home equity loan or refinancing.
2. You could fail to save for retirement, which is an obligation you have to society. Again, you won't see the effects of this for decades, when you retire and realize you are a pauper.
3. You fail to save for "emergencies" (which are actually contingencies) such as car repairs, health issues, home repairs, and other unexpected (but expected) expenses. Again, you may not feel the effects of this for years, even decades, until you are blindsided by such an expense and then have to resort to toxic debt arrangements.
4. You spend more than you should in retirement and run out of money before you die. Again, you may think things are going well but two decades later, you realize too late that you shouldn't have bought that shiny new motorhome or fancy boat.
Another alternative requires setting up a budget and sticking to it. Once you start budgeting your money, you realize exactly how poor you are even if you are making six figures. The couple in the link above were lucky in that they were able to communicate with each other and agree on a plan of action and make sacrifices for their own future. Many couples can't do this and opt for divorce (which is even more expensive!) rather than sacrifice. Too late they find out they screwed each other royally.