Unless you are reasonably sure of your conviction to either buy, sell or hold, it is better to observe the market from the sidelines until your confidence improves. Once I refused to buy soybeans because they were seven dollars. I was bullish and so was the market, but seven dollars was a price I had never seen before in beans. Subsequently, I watched the market go to 13 dollars. Put your trust in the markets, and do not be afraid when they reach historic highs or lows.
Markets are where they are for a reason.
Evaluate that reason on its own merits, and except the inherit unpredictable qualities of speculation. When too many market participants are moving the market in any one direction, the market becomes very vulnerable. Also be sure to pay attention to the makeup of these participants. Never underestimate the makeup and volume of the market participants. Only when put in the perspective of the basic main trend do minor fluctuations have any significance.