What I learned in ATL airport: be prepared, don’t make this mistake!

I was flying home from Houston Texas last week and had a connection through Atlanta airport. One of the busiest airports in the world… I took the tram to Concourse D and decided I needed a bite to eat. I stopped by one of the diner food establishments… In general I try to avoid fast food when I can, but their registers were all down and they could only take cash.   What does this have to do with opportunity?