There are some human weaknesses as greediness, hurried decision, impatience and to become rich in a night. Having these, we buy a big trade for earning a huge profit, to average a trade avoiding loss, occurring some wave and market ups and downs. All these facts result in the liquidation of an account and loss of money. These weaknesses can be control in a limit but not completely.
Even 1/10 is a lot if you are an intraday trader but I get your point and I agree with it. There will be maybe 10-20 trades you do inside of a day if you are that kind of a trader and not all of them will be profits, plus each day may not be same, one day you will lose $30 the other day you make $50 and you can keep doing this for a long time, what is important is your average, what do you make in a week on average?
If you do this for a whole year, and check how much you made total in profit, you will be capable of knowing how much you can make in a year, the amount is not even important because you should look at % how much you made. However sometimes even years do not count, look at this year, many people made a profit, but look at 2018, many lost. So it is the long term, even if you make 10-20 trades a day, still the long term is more important.