In the old days, when Jim Cramer was on Wall Street, it would take weeks for investors to unwind decisions they made and change their minds. These days, buyers and sellers are making decisions at lightning speed.

When the tragedy in Brussels occurred Tuesday, stocks collapsed immediately. Then, slowly, segments of the market that had nothing to do with the terror attacks began to rejuvenate, led by health care. Then tech came back, followed by domestic utilities and international growth stocks.