Buy when prices are low and sell when prices are high. It works just as long as we can be patient. We should be calm when the price falls because it will rise again. Provided that we have a strong capital, this can work well.
For bitcoin, yeah and sometimes you have to also be careful and watch out for some breakout movements which is where most newbie traders miss it. However, for every peak there would always be a correction, and after every correction, there should always be a rise at some point. The good thing about bitcoin is that if you miss a moment, you can get it back in another.
I will suggest you not to sell all your bitcoin. The best practice which you can do in this aspect is that you can sell few of your bitcoins and then you can re-invest that money into bitcoin again as well as you can make something productive out of that money. The rest of bitcoin, you need to keep them in your wallet as the market price of bitcoin will rise high in the coming days as well which actually means more profit.
Even in trading normally, it is not advisable to go fully in on a trade. You should always keep some back just in case so you won't miss another good entry probably on the same trade or another trade. The thing is for someone like OP, they should always have a strategy and not just trade or make decisions on trade like they are gambling. There must be a set out plan before any move at all.