I have used many strategy to trade but I still run at loss and that was why I decided to stop trading because of the risky involved in it. Professional traders don't make profit everyday even upon that they understand the market more. Bitcoin market is too complicated for anyone to understand it all and that is where traders make mistake at loss because they think that they have understand the market fully. Only trade with the amount that you can afford to lose.
In my opinion tradin can be profitable, provided you know how to set take profit and stop loss. I have fair share of trading experience of running into both profit and loss, whenever I have lost a trade it's purely because of my mistakes like selecting some shit coin just because it pumped or becoming too greedy and not setting stop loss. But if you trade in Bitcoin the risk of running into sudden loss is very minimal unless it's a sudden dip which happens very rarely in Bitcoin. Full time trader has their own strategy and as you mentioned even they may not achieve profit everyday but they do definitely earn profit even if it's a week long, month long hodling which we don't forecast.
It's simple that follow certain rules by creating them like percentage of risk taking, when to take profit and which coins to invest, number of traders per day. These are hygiene metrics of trading because most of us losse due to not following it