I'll check out the post you mentioned and comment if I can think of anything useful to add.

The facts are like this - over 90% of traders fail, and lose all their money. To be in the 10% that do make money, you need to be thinking and doing the opposite to those in the 90%. That's pretty much the secret to it all :-)

Interesting fact for example, take a moving average cross system, something simple like the 9 SMA crossing above the 20SMA as a buy signal. Very common type of system that's recommended to newbie traders. Try backtesting it, it never ever works out profitable.

So what do you think happens if you always sell when you get a buy signal ? ;-)