My husband, the software developer, introduced me to the term technical debt. As I understand it, it basically refers to situations where there is a difficult coding problem to solve that has a Takes-a-Long-Time-to-Do-it-Right way and also a Fast-But-Good-Enough-for-Now way to write the code.
There may be a time or money deadline that calls for getting the work up and running now. A developer might then use the Fast-But-Good-Enough-for-Now method, knowing they have now incurred some technical debt that must be repaid. Meaning, sometime in the future they'll need to go back and write the code in the long-term-sustainable way.
It is not inherently bad to incur technical debt. It just needs to be periodically repaid. If not, well, bad things can happen in the software/system.
It occurs to me that many people have racked up a pile of unpaid health debt. Not getting enough sleep, eating poorly, constant high stress... add your own issue to the list. I've been guilty myself of this - pushing myself and not paying my health debt until my body revolts and I get a nasty cold or an injury.
Everyone is different so sustainable levels of health debt vary, too. The important thing is to start noticing when you are increasing your health debt and when you are paying it down.