How would you prepare/keep your brain sharp for an important, make or break meeting later in the day?

  (make-or-break)

I think whatever it'd be, I'd just 'stay in the moment' --  it's all we've got. I try t olive most of my life that way. And when I concentrate on the moment, I tend to relax and things go seemingly better.
:)
Best wishes if you have such a meeting!
:)

maybe you should pray before the meeting

I'd solve algebra problems - I find that it is a good way to get my brain thinking. Cheers!