Best Lesson Learned from Adverse Situations...

[Andrew Ginsburg]

During the latest and greatest podcast featuring Jay Papasan, Jay brought up an interesting point made by Trump that he learned nothing when the markets were good and everything in down markets (I'm sure I butchered the quote, but I was driving and wasn't able to write it down!). As a newbie, I am finding great information here and really enjoy the success stories that are shared. Obviously I don't like to focus on the negatives, however sometimes we can learn just as much if not more from the mistakes we make. 

What was the best lesson you have learned from a mistake in your REI career, or when a deal didn't turn out as planned?

I apologize if this is an unoriginal thread and has been discussed before!