What is more required during a sideways market is frequent evaluation of your strategy, keeping your emotional balance in check, and not getting into too many trades.
The sideways market occurs when markets are not dominated by the large players and instead traders attempt to dominate the market and keeps the market in a stable range. These are the phases where breakout failures are very common.
Sideways markets occurs if there is no real interest neither from the buyers nor sellers. Lower trading interest results in lower transaction volume. If the sideways action attracts huge volume possibly it could be due to institutional accumulation/distribution.