The ups and downs of the stock market can be very difficult to make sense of, but in a general sense it's true that stocks are more expensive when the market is supposed to be doing "well". Yet buying such a stock doesn't guarantee that it will actually yield any real return for the buyer. It just doesn't seem worth it to me.
The stock market is a high currently, but not quite at levels from 14 years ago. According to Forbes, "A comparison of stocks with earnings tells you that the market is overvalued by 40% to 50%." Some of the rise in stock prices is caused by the economy and companies expanding. This only accounts for a portion of the increased prices we have seen in 2014.
Yes, stocks are expensive now. However, it does not necessarily mean to sell away your stocks. There are other factors to consider when determining if stocks are expensive or not. The most important factor to consider is the economical growth. The economy and businesses are growing, so stock prices are expected to raise.
Though stock prices seem to be on the rise, the price-to-earnings ratio is well above average, indicating long term growth and a better value, even at a higher nominal cost. Though there is concern that we may be in a bubble, the rise is consistently upward, and holds hope for US stocks.