None, can you guess for any length of time your heart will keep beating?
Back testing gives probabilities however in life anything can happen any given time. Intraday to using monthly charts, all you can somewhat control is risk(amount to risk) and risk management(whether the signal is valid based to the left of present and managing trade in present). If you can reasonable control "risk", trading is like flipping coins, more chances of doing, eventually you end up profitable outcomes. If you can control risk well, losses decrease. Decrease losses means lower drawdowns to me and less to make up.
I applaud those who do so well at swings, but I prefer to stay in.