There's a lot of proof to support that. But it is overly simplistic.
My emotions got the better of me yesterday and I was up about $6k at one point. I was above the point I would happily have sold at earlier so I should have sold right ? I actually ended up losing all the gains.
This is not a technical trading issue - its am emotional/psychological issue and there must be traders out there who have dealt with this and overcome it. I would like to know what it is they do to avoid riding a SP up and down and not capturing a healthy part of it.
I'll bet most punters go broke for this as much as any lack of technical skill