[When] the market is trying to get to terms with, first, lower global growth, particularly out of emerging markets and China. And, second, the market is worried the central banks have run out of ammunition. So put these two things together, and then investors are repricing the market lower.

Investors should be cautiously positioned as the global economy and markets face major uncertainties. The downgrade will be a further headwind to growth and job creation in the U.S.

[When] the market is trying to get to terms with, first, lower global growth, particularly out of emerging markets and China. And, second, the market is worried the central banks have run out of ammunition. So put these two things together, and then investors are repricing the market lower.

The one instrument that has relative political autonomy is monetary policy. Central banks do not need to go to Congress to get approval for an interest rate hike.

Investors have to ask themselves two questions. How much can we grow our investments? And, can we afford our mistakes?

Investors should invest on what they know. The biggest mistake is to invest on what they don't know.

The world changes! So we're in a situation today where the only policymakers that have flexibility are central banks. But they don't have the instruments! So they've had to experiment, and the more you experiment, the more uncertainty and the higher the risk of collateral damage.