Please my opinion is to take that advice with a pinch of salt because when you have spent years learning the skill of trading and it doesn't seem to go well for you, I advice you get some other skills that might work for you.
The phrase in the "persistent" as a required exercise in trading doesn't mean to treading endlessly. It's just a key point that'd encourages your enlightenments to learn from your experiences.
And your trading strategies in the prediction markets may not be guaranteed nomatter how strong is your confidence. It's practically a market of try your luck with your own strategies. So your inputs and results will tell if you're advancing to locate the winning points as a beginner and so forth, the positive outcomes will prompt you to be persistent even when you're loosing because you're already seeing your improvements.
It's all about courage in other words, trading uncertainty might be related to gambling where lucks maybe required and consistency might someday bring you the wins.
Trading hasn't been for for everyone so, anyone who sudden jumps out of trading as a view of carrier because of consistent looses made the wrong decision from an earlier stage otherwise, loosing shouldn't make you opt out because before you get into the market, you should had been aware about the risks which is where it knowledge is expected to be acquired first before riding on.