It's not easy to tell whether the market is overvalued or not. Right now if you believe interest rates and inflation will go up within the next few years to anywhere close to historic norms then the market is probably on the hot side. But if rates stay low for very long durations then the market isn't hot. Also international markets have lower valuations than the US so you get something out of diversifying there. You could consider a little less stock in your mix these days but shorting the market would be an extremely risky proposition - more of a gamble. In the long term even if the market is hot and corrects you're still going to do OK.