I think better strategy would be Buy the DIP, sell at local high, open short, HODL and sell at local low. Rinse and repeat. Indefinitely. Yes, it is easier said than done. But for me, it is easier after around 6 months of watch, learn, and execute.
This is completely an off topic and meanwhile this thread is not talking about selling which sounds more of trading and gambling, but accumulating Bitcoin and hodl for a long period of time for like 5-10 years and the best way you can do this is to set aside an amount of income after setting aside your reserve fund or an emergency fund then use to amount to buy Bitcoin by using the DCA strategy which will help you to buy at regular interval either weekly or monthly.