As he refrains from using the memorable phrase *irrational exuberance* to assess bullish investor sentiments, former Fed chairman Alan Greenspan discerns asset bubbles in the American stock and bond markets in early-2018. Despite the recent healthy fundamental recalibration, Greenspan warn of high U.S. stock indices from Dow and S&P 500 to NASDAQ and Fortune 500. Also, Greenspan points out that the current government bond yields hover not far from historically low thresholds. The latter may transform into potential U.S. bond yield curve inversion, which often signals the early dawn of an economic recession. This inversion correctly predicts U.S. economic downturns in all decades after the 1960s. As the Federal Reserve gradually normalizes and tightens its core monetary policy, interest rates continue to raise the relative likelihood of bond yield curve inversion. Greenspan shares his ingenious insight that higher long-term government bond yields may determine the extent and duration of bullish investor sentiments during the current interest rate hike. Whether the Trump team addresses the fiscal gap with $2 trillion government expenditures and $1.5 trillion tax cuts depends on the future U.S. real GDP growth trajectory. The Trump administration expects 3%-3.5% real GDP economic growth for this self-finance to trickle down to the typical American. Greenspan's prescient comments warn of the current fiscal shortfall that may fuel U.S. debt escalation as a proportion of total real GDP.