
The rule of only being able to make one trade per day in real trading and one trade per stock on the chart game is something that gives you tremendous power: you know there's no rush and that you'll be able to pick the best opportunity out of plenty of opportunities. It's a rule that encourages you to be
picky, and it totally removes impulse trading. There can be no impulse trading if you are required to discard a majority of what you perceive as "opportunities". But can we still do this once we start making money almost every time we trade? Well, the trick I think is to still be "picky" no matter how good you seem to be and no matter how many opportunities you feel you're missing. You've got to feel as if you're
wasting opportunities. The fear of missing opportunities is what makes you overtrade, trade compulsively and similar. By only allowing one trade per day, you know from the start that you will waste most opportunities, and you'll get used to picking the best opportunity there is. Furthermore it encourages longer term trades (since you won't feel like staying out of the market for the rest of the day), and to let profits run, since if you get out, you won't be able to get back in (and you'll miss the larger move).
In particular it gets rid of these things:
1) revenge trading: if you lose or miss a profit, there will be no more trades available to make your loss or missed profit back.
2) overconfident trading: if you win, there will be no trades available to return what you won by trading carelessly because you feel infallible.
3) doubling up on losers: if your trade is not going well, you won't be able to add it to by buying lower or similar. It either succeeds or fails, but you can't add to it.
4) hesitating when you're losing: you won't be tempted to second-guess your trade and exit early, because that's the only trade you can make today. But also, you will think about it more and choose more carefully, so you'll be less likely to have doubts about it.
And, the next day, whether you won or lost, you'll be over it.