I would not says every time is being missed because to get the perfect timing is like either you exactly know that this situation will be happening or else it is just a coincided that you buy and prices drop or rise vice versa. Also many things are not in one's control so timing the buy/sell would I say may not be at all easy job.
It's impossible to sell at the top, or buy at the bottom if you just wait for the right moment. That's why you should buy/sell in smaller percentages. If you do that, then you mostly do sell at the top and buy at the bottom. It's important to never sell all your coins at once, or to buy with all your money at once. That way you will never fully benefit from whatever direction the price is heading to. Be smart.
You are right! I always missed because i like to sell all my btc at once or buy all with my fund ,like this time I missed the btc train again as I sold too early