There is no ideal or correct time for investment. Every time is appropriate if you want to invest long-term. Whoever bought at 2017 ATH can sell now and his investment will have been lost, but we can say that this time is the best time to achieve the maximum possible profit in the shortest possible time?
In theory, it is correct, but the price may be in the area between 25 thousand to 32 thousand at some point in the beginning of next year before the upward line continues. Therefore, now is an appropriate time to achieve maximum profit, but it is not the best.