Good advice, whilst I talk a lot about backtesting and using demo accounts, there's no substitute for having skin in the game for experience.

Some people just aren't cut out for trading, they may have the best will in the world and maybe great at picking stocks, but just can't handle the emotional stress of being in a losing position.

I'd add the following bit to your advice, decide beforehand on a price or condition that means you accept you've made a mistake, and get out. Losing trades are part of the game, as long as you don't stand frozen in fear as it plummets to zero :-)