The economy is a very complex beast, and every time I think I'm starting to understand it, it changes.
One theory that I tend to subscribe to though is that we now are driven more by credit and debt cycles than by the past understanding of normal economic cycles. This is a link to a series of short articles that expounds on this view. A recommended read for those who like to look behind the curtain a little further. I don't agree with all the points of view in these, nor claim to be versed enough to agree with or rebut the detailed specifics, but think that there are a lot of facts and good information here that you'll never see in the daily mainstream economic reporting.
One premise is that corporate debt has gotten out of hand and some of the shakier elements are coming due soon. Also, that easy credit in general has just become a really big issue, even post-2008 (up to 2008 or so it was most egregiously applied to housing):
First in series:
http://www.mauldineconomics.com/frontlinethoughts/credit-driven-train-crash-part-1
Later in series, with links to the other prior weekly articles near the top right after the subscription plug (which can be easily ignored in each article):
http://www.mauldineconomics.com/frontlinethoughts/unfunded-promises/P10
I've found these types of articles often to be correct about a lot of things, but even by their own admission, the timing to react to it is very difficult. Those of us who read these may be early in understanding (if not always savvy in reacting), because it can go on a lot longer than you think, and it often just continues until it doesn't. As others here said earlier, timing is possible, but takes a lot of work and deeper understanding of what's going on out there than most of us have time or expertise to figure out.
I will stay away from more bombastic commentary other than to say look at when the booms occur and why, when the busts occur and why, and who ends up cleaning up the messes. Then draw your own conclusions.