Gartman admitted he's tried to fade the rally in the past, along with other "smart" people, but said every time he does that, "it's been wrong."
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On Wednesday, minutes released by the Federal Reserve from its July meeting showed that some members of the Fed's Open Market Committee want to make a "relatively prompt" rate hike. Most members agreed more data was needed before moving up the rate hike schedule.
Despite that news, U.S. stocks climbed mostly higher on Wednesday. On Thursday, the market ended up, with the S&P 500 toppling another record.
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"I think you are now in that period time when you are going to see interest rates beginning to rise and stock prices go higher," Gartman said.
In a about a year or two, when "all of a sudden everyone is euphoric" and capital expenditures increase, stock prices will start to decline, he said.
—By CNBC's Michelle Fox