xdude, Wow,'The Sunk Cost Fallacy' theory sounds a LOT like my "two dates to soul mate" rule....
If I am not absolutely smitten with someone (and they with me) at the end of our second date, I won't go out on a third date. I move on. A few years ago I figured out that when I consider all my failed relationships in life (quite a few, I'm in my 40s), I knew everything I needed to know about why the relationship would not work by the end of the second date. Which means, every date after the second date just set me up to feel like I'd invested "so much" in each relationship that I ought to stick it out and not throw away my time, energy, emotion, etc. that was already invested in the relationship!!
Dumb reason to stay in a relationship, but EVERYONE does it. Everyone. And, for me, it meant I married a man that at the end of our second date, I had serious doubts about, yet, he asked me out again, I accepted, then again, I accepted again, until before I knew it, we were engaged, then married, and by the time I came to my senses, I was in the middle of a living hell married to a bipolar man (didn't know he was bipolar until a couple months after we were married) who decided to stop taking his medicine after we got married and start wailing on me instead.
I know this probably won't help losthurtused today, but in the future, it might avoid doing the same thing again hoping for a different outcome. We all do it. We are human. We throw logic out when dating when we ought to throw emotion out and use logic only.
~A