Buy low, sell high... seems simple, doesn't it?
unfortunately as this OP demonstrates, people tend to do the opposite because they invest at the whims of sentiment. They but the hot investment that has gone up over the last few years, get fed up of it when it doesn't perform to their expectation and end up quietly discarding it somewhere around the bottom.
IMO swapping your gold for stocks right now is about the biggest mistake you can make. Not because I think the USD is going to collapse tomorrow and take all paper assets with it, but just from a sensible asset allocation strategy.