Not all markets have upwards bias. Nikkei has not reached its alltime highs in decades. Also, lots of companies go bust and new companies come in. Even if market cap of the index stays the same you can still lose if this the case. But all things aside, if you pick a stock that has a upside bias in the long run. Yeah, basically you should have positive expectancy regardless of any profit taking/loss cutting ratio. Of course if you have an extreme ratio its is not practical even though its mathematically nett positive. You could have 99 losses and that 100th trade will cover your 99 losses and +1.