The British fought three wars in Afghanistan over an 80-year period. They finally left this “graveyard for empires” in 1919, only to eventually be replaced by the Soviet Union in the late 70s, and the U.S. in the aftermath of 9/11.

The great investor and writer Andy Kessler frequently points out that the failure rate among Silicon Valley start-ups is 90 percent. Every member of the economics profession would be wise to memorize the previous figure, and repeat it daily. If so, economists might come closer to understanding why they’re mystified by what they deem slow economic growth. And mystified they are. So much so that they’ve apparently given up.

Every day there are legions of new economists who dismiss the Donald Trump economic agenda and his forecast of 3 percent growth as a wild-eyed fantasy. The consensus is that the economy “can’t possibly grow at 3 percent” says The Wall Street Journal. “Slow growth is the new norm, so get used to it,” writes Rucir Sharma, Morgan Stanley, chief global strategist at Morgan Stanley in Foreign Affairs magazine this month.

The stock market has risen about 9 percent since the election of Donald Trump with near a $2 trillion increase in wealth. Is this the start of a big bull market rally? Investors are rightly euphoric over President Trump’s pro-business/pro-investor policies. But Wall Street is coming to grips with the political reality that gridlock is the default position in Washington. Democrats have announced they are preparing an all-out defense against Trumpism as if they were trying to repel the Normandy Invasion. So the market has been jittery in recent weeks, rising on Trump successes (such as the regulation roll back) and falling into despair when his economic agenda seems bogged down or he pursues bearish policies like tariffs on Mexico. To get a sense of where the market is headed, it’s wise to look at the historical parallel of the early years of another presidential disruptor: President Ronald Reagan. Mr. Trump can learn from Mr. Reagan’s mistakes and successes.

Like Reagan, Trump should act quickly—and with a bill that can achieve bipartisan support.