Toss a coin a hundred times. Most likely, somewhere you’ll get five tails in a row: that happens in about 8 cases out of 10. The coin isn’t broken — it just happens.
Say you are right in 4 trades out of 10, and you make twice as much at the target as you lose at the stop. That’s a working strategy. But over 50 trades it will in most cases have a streak of five losses in a row: that happens in more than 8 cases out of 10. And a streak of six — in about six cases out of ten.