If you'll bear with me through what seems like an unrelated tangent, my dad used to say about planning vacations abroad that the important thing is to enjoy each day, rather than try to see every attraction and come home exhausted.

That wisdom has implications far beyond trip planning. In investing, for example, the important thing is to find good investments at good prices, rather than try to invest in every opportunity.

O'Leary didn't invest in Doorbot, and lost out on hundreds of millions of dollars. But how many hundreds of millions did he save by not investing in other things where he didn't like the price? And how many hundreds of millions did he make by investing in opportunities where he did like the terms?

The real lesson here is that you can be successful if you have a reasonable system for deciding which opportunities to invest in and which not, and implement that system consistently.

Doing this, you'll miss some opportunities that would have made a lot of money (false negatives) and you'll invest in some lemons (false positives). However, far more choices you make will be true positives that make you a lot of money or true negatives that save you from losing a lot of money.