It's impossible to predict in advance just when the best and worst returns will occur in share markets. For example, the worst one-day return on the Australian share market in the last 15 years happened on 10 October 2008, when the market dropped 8.3%. The very next business day, the market rose 5.6% - the second best day in the last 15 years!
Anyone trying to time their investments to avoid short-term losses could be just as likely to miss gains. Over time, missing just a few days' sharemarket performance can significantly reduce the overall performance of your investments.