What would you say many people or most people fail to do that would benefit them if they did?

Find  a passion for something.  In the best of scenarios once found, make a living doing it.  That's almost too much to hope for but it happens.  

They fail to think for themselves.

If it isn’t verboten to respond to one’s own question (anyway, the hell with it if it is) my point would be that people consistently fail to use their time constructively. They waste time waiting around, standing around, passing away hours in idle, even self-destructive pursuits. They take the very essence of life for granted. What’s worse is the example of those doing so buoyed by the pretense that something better surely awaits them in a supposed “next” life. Life as a dry run, if you will.

What people get wrong is that they could be improving their lot, their family’s lot, or some aspect of the world around them, but for the sad inclination to laze about squandering hours, days, and years that grow ever shorter. 

(Puts soapbox away) This post was edited by Don Barzini at July 10, 2018 5:59 AM MDT

I'm going to say ... stop prying in to other people's business, and examine their own values (and if they live up to them).