I agree to you, counting those mistakes will help you to be a good trader but that's part of being used to the market. As you become used to the market, you're gaining experience and that's included on it.
Open order is executed due to volatility as soon as the market is open to understand the trading market in advance. An experienced trader can go to profit by making perfect judgment at this time. But apprentices are advised that the first 15-20 minutes of the market start, the time between market hours is less volatile to understand the nature of market movement and the volatility is seen to be revived as the last hour approaches.
Even experienced traders, they are having a shortcoming with trading. It's not that everyone is secure with profit and despite having the experience, they still make some mistakes with their trades. Mistake in a way that they're losing a trade and didn't anticipated some overturn has come. This is very normal and about the market hours, it is 24/7 open so there's really no connection to it when you've become reliable trader. Whether you trade day or night or you have some allowance in time, still it's all up to you.