What exactly makes you think so? Bitcoin is currently down ~60% from its ath ($69k), so how can you claim it has never lost in the long run?
What you mean is that historically Bitcoin's price moved in cycles, with each cycle bringing new ath, but, as the things currently are, you cannot say that it has never lost, as that's simply incorrect.
Also, the belief that the price will keep moving in the same pattern forever is naive. It's simply not possible for it to move by a similar percentage each cycle, as everything has its limits.