The Sunk Cost Fallacy: How It Affects Your Life Decisions
The sunk cost fallacy is a cognitive bias that makes you feel as if you should continue pouring money, time, or effort into a situation since you’ve already “sunk” so much into it already. This perceived sunk cost makes it difficult to walk away from the situation since you don’t want to see your resources wasted.
What if your relationship partner got badly sick and becomes more of a weight than before? Should you disregard what you have lived together because it is accrued and leave them because it is going to get worse in the future?
Depends, honestly. that's far to vague a scenario to give any solid answers.
but again. while we're using terms like "costs" and "benefits" don't forget, one of the "costs" involved could very well be one's own self respect. as well, there's other benefits, like still being with a loved one. Just because it's intangible doesn't mean it's without value.