Focus is being clear about what we want and what we are going after.

And ignoring everything else.

The first part is the easy work. Introspection and investigation is all we need to be clear about what we want and what we will go after. 

It is the ignoring everything else part that trips us up.

Every opportunity that we comes across seems like a once in a lifetime opportunity. And we're afraid of losing out on something that could be big or important for us. 

And that is actually true. By only focusing on what we want and ignoring everything else, we do miss out on opportunities that could be big or important for us. 

But the alternative is even worse. By always keeping an eye out for anything and everything that could be important, we de-value the importance we associate with any one thing. And we end up pursuing several red herrings and dead ends. 

Our focus need not be set in stone for the rest of our lives though. 

We learn as we go, and adapt as we go. 

After all, survival of the fittest is about who adapts the fastest and not about who is the strongest or the "best".