I think you should buy bitcoin today. it's never too late to buy bitcoin. maybe the price will go down but it's only temporary .. and the price will come back up. if you ask your moment to buy bitcoin .. maybe it is very easy for bitcoin. you only buy bitcoin at a cheap price and sell it when it is expensive. but you should not sell it .. keep your bitcoin in a long time so you get a lot of profit. do not wait for bitcoin prices to go up as you will regret in the future.
You are right in one aspect. But the general trend which is being followed when comes a point you need to decide amongst buying and selling of Bitcoin is grab as much as you can when the market price is down and do not sell until and unless you have achieved that much profit which you want to earn. I think this is what the bottom line is.
I think those who can sell their portfolio at right time are always in profit because if the price is high then the rate you have purchased the portfolio and you did not want to hold it more for more profit then you will be very safe from the decrease in the prices of your portfolio and by selling the portfolio you will be able to prepare the new one which can also give you profit in near future and the vice versa like if prices are going down you sell it to avoid further decrease.