I think the answer is, beforehand there are too many contingencies and it seems like a waste in mental effort to consider them all.
Consider the stock example, which is quite simple. I buy a share at $100. I don't think it's so simple that I decide in advance I'm going to sell if it drops below $80. What if, in one day, it drops to $83, and I don't have access to a broker except to sell it at the end of the next day? What if the stock is doing well, and then there's a rumor that quickly sends it down to $80? What if I happen to have good reason to think the rumor is false? What if it's doing very well, but then a rumor sends it down to $85? And this time, I think the rumor is correct. What if I'm away from my broker while bad news develops and it drops to $50, but then the bad news appears increasingly not so bad and the stock is rising when I get in contact with my broker again? Etc.
And all this has to do with when to sell a share of stock, which is seemingly characterized by a single number. There is much more that can develop in connection to the scenario you describe.
Mark Cuban assumes you and the seller are the only people in the market. If there are lots of traders, then the trade price is set by some average assessment of the stock value. Cuban also assumes that you want to buy the stock because you think it's undervalued, and the seller because he thinks its overvalued. But maybe the seller just needs cash, or you just want to invest.
A paradox of economic equilibrium theory is you shouldn't have to do any research: the "invisible hand" of free market should guide all prices to their correct value. The paradox is the theory assumes everyone is fully informed and rational, which seems to conflict with the ability to avoid doing any research. The reality is a more complicated and nuanced picture, which is why I'm surprised how forcefully some people defend free market fundamentalism.
I feel for you. I was raised Catholic and was quite religious up to and through high school (people considered me "mature" in faith). As I matured intellectually, my faith became increasingly abstract, until at some point in college I realized it would all be simpler if Christianity were basically false. Unfortunately, at least in my experience, once you take seriously the idea that a religion is false, faith quickly becomes silly and there's no going back.
I am still struggling with how to inform those around me of my changed perspective. My family is of course Catholic, but my in-laws are Evangelical. My rather cowardly strategy so far is to slowly inform people, when the timing seems appropriate. I told my wife a couple years ago, and discovered she was struggling with similar questions. This was a fortunate coincidence, I guess. I've told some of my siblings, in confidence, and am just waiting for the right opportunity to tell my parents. My wife and I are still too worried about hurting her family by informing them.
So sorry, no advice, since I'm stuck with similar dilemma's as you are. But just thought to let you know you're not alone.
Nice post. I agree very much. This simple observation goes far to explain trends in how beliefs about religion, politics, race, and gender are handed down from parents to children.
It took me all the way up to graduate school to break the molds of childhood on my political and religious beliefs -- and I was helped by a number of factors that most people don't experience: living away from where I grew up for many years, having unpleasant childhood experiences that I prefer to separate myself from, and, if I may say so, being a very intelligent and critical thinker, at least by all the standard measures.