I can't agree enough. Most (95-97%) of my investments are low-cost index funds. My strategy is built roughly off this article (http://www.forbes.com/sites/thebogleheadsview/2011/01/28/thr...), adjusted for what I see as my short, medium, and long term goals (eg okay with some money in riskier, higher-return target assets for retirement savings, some more conservative things for saving for house downpayment, etc).

That said, I do the occasional amateur stock trade with a small amount of funny money. Much to your point and the OP's point, these often go against me despite my hunch. CF my recent purchase of TSLA at $145 ('buying at the bottom') and my recent sale of bitcoin at $350 ('sell before the crash and buy back in').