The reason why investing is so hard has its roots in what actually is investing. Investing is basically a legal way to utilize capital to gain at the expense of peer investors and future investors, as well as other organizations in the society. Therefore a huge amount of human brain power is being applied to accomplish this competitive game. Not only that, human emotion factors play a significant negative role along the way for investors. Investing is actually a bit like brain surgery, which also needs a lot of knowledge, training, practice and perfecting. Yet this is a game we cannot afford to lose and cannot afford not to participate.
Time spent on predicting is usually far more than its usefulness warrants. Instead, investor ought to focus on planning the reactions to future events, just like planning for a vacation in a foreign country.
Over trading is a universal mistake for traders, experienced or not.
I wouldn't be surprised if the S&P 500 index is 500 or 2,500 tomorrow, -both are 'reasonable' even from valuation point of view. This is one reason why investing is so hard, because the rabbit can appear anywhere anytime. Some people choose to chase the rabbit all the time, and some prefer to wait for it at a fixed spot, yet some others set up traps in various spots.