Some day in the future, you will realize that the best time to invest was not today, but some other day in the future, when prices were low. But with the information that you have today, the best time to invest is still today, because you do not know when prices will be low, and you do know that the longer you hold your investment, the more time it has to grow.
Toughts?
The best time to invest in bitcoin is when the price of it is low or decrease, but we don't know when will the price will get low. But if that day come, you need to buy bitcoin because when its value rise again you will have now a profit. And when you wait 'til the price of bitcoin become so bigger and higher, it was a pleasure for you. So that your money will increase too.