President Trump promised to increase economic growth to 4 percent. That's faster than is healthy. Growth at that pace leads to overconfident irrational exuberance. That creates a boom that leads to a damaging bust. The factors that cause these changes in the business cycle are supply, demand, capital availability, and the market’s perception of the economic future.
Overview
U.S. GDP growth will slow to 2.3 percent in 2019 from 3 percent in 2018. It will be 2 percent in 2020, and 1.8 percent in 2021. That's according to the most recent forecast released at the Federal Open Market Committee meeting on December 19, 2018. The projected slowdown in 2019 and beyond is a side effect of the trade war, a key component of Trump's economic policies.
https://www.thebalance.com/us-economic-outlook-3305669