With a lot of stocks hitting new high prices, both the SPY(-1.42%) and QQQ(-1.78%) still had a sell-off day. Sell-off (or distribution) days are typically healthy for the market, except when too many accumulate. With that said, many distribution days that the QQQ(-1.78%) has will become insignificant this week.
The stock market is in a short-term uptrend, but the fluctuation between sellers and buyers in recent days is indicating a stage three sideways limbo movement. It will do you good to stay vigilant and use your stop-losses to minimize possible loss.