It is not always easy to sell and buy back that way. You can easily sell when there is big profits and leave the money in stable coins or fiat but the challenge is buying back because the entry point will become very confusing. During the recent retracement, many people were waiting for price around $50,000 as they thought it will go that low. Most of those people did not get their orders filled because price did not reach the area they have the buy orders and if price continues to rice higher as a result of the recent bitcoin halving, they will miss the entire gains they would have made because they sold so early. Buying low to sell high is better is it is planned across market cycle and not in a short time when price has already taken off.
I agree with you on the difficulty of buying back when you sell at profits, s9me time if you are not carful you may end up losing all the profits that you already accumulated from selling at the top.
Other hard aspect of that is when you buy back and the market slid back further, that point you lose more and more until you possibly lose all the earlier gained profits, so in general it very hard to apply that approach most especially for newbies.