Do I have to be able to foretell with absolute certainty in order to win? No. If I have a coin which I know comes up heads 60% of the time and I am allowed to bet with that coin and I get to pick which side, there's no way I'm not profitable over a long series of bets. Simply bet heads every time.
Will I win the next bet? Unknowable. But knowing I will win three out of five on average means I will through smart betting be very profitable in the long run, certainty be damned.
It is always that 1% that people believe it will never happen to them. I designed a system in 90s that was profitable 40% of the time, then I hit the mother of all losing streaks, 23 losing trades in a row, taking the 24th trade was as easy as taking the first trade as I knew the 1% could happen, and was well financed for this system, next trade was in Coffee and took care of all the losses and then some. We never know if next trade will be a winner, and like your magic coin, we keep trading as we believe in the numbers.
i'm somewhat of a baby in this 'game', compared to alot of you old farts who've been lingering here for a while.