The rebound in the stock market following Wednesday's interest rate hike may already be over. The SPDR S&P 500 ETF Trust, which tracks the broad stock market, stalled out at important resistance.
As you can see on the following chart, SPY reversed off of the $430 level. Savvy traders were expecting this and here’s a logical reason for it: This was a support level, and support can turn into resistance.
This happens because of buyers' remorse. Many of the investors who bought SPY at the support now regret doing so because the price is lower. A number decide to get out, but only if they can do so without losing money.
As a result, they place their sell orders at the same price they bought at. In this case, it’s $430. If there are enough of these orders, it will convert the level from support into resistance. That’s what happened here.