Of course there is no 100% sure thing. Trading is about taking risks based on probabilities, not reading crystal balls. Nobody knows for sure, but most experienced traders could have told you in early 2018 that we were probably entering a long term bear market.

Things are a bit murkier now that we've dropped 84% from the ATH, but it's still safer to keep betting on the downtrend. The trend is your friend until it ends.