Bitcoin price never goes down 20% daily as you said first of all. You can say like 20% rise per day and that happened last December, you should buy when price is so cheap and if you already bought it just hold it until it rises up as expected price by you. There are many reasons for dip or rise and nobody can predict exact price for future in cryptocurrency trading.
I think that it's better not to pay attention to the forecasts that sound for the future of Bitcoin. You need to be guided by the current events. If you can earn on the difference in price, then you need to do this. All the same, but Bitcoin rises at least a few percent and goes down, for the day and every day.