selling to buy back cheaper is a dumb idea, and it is contrary to what any newbie should be doing. We should tell them that is dumb.
Selling lower than you bought is a dumb idea, so we should tell them that is dumb.
Failing/refusing to continue to buy at a reasonable rate is a dumb idea, so we should tell them that is dumb.
It is good that you are saying this, even if it sounds like a bitter truth, and most newbies must have fallen victim to this in a bid to think that they are being smart.
Rushing to sell below the price at which one bought his Bitcoin is dumb. Even from basic economics, when the selling price is less than the cost price, it is only foolish to sell at that price except you are dealing with a perishable asset that can't stay after a certain time. Is Bitcoin in that category? For Bitcoin, even letting it stay is the best way to remain in profit, which makes it dumb to think of selling too suddenly.
Even if you're in profit i.e the price off bitcoin is higher than your entry point, you shouldn't think of selling until you have over accumulated more than enough Bitcoin in your possession. Any investor in his accumulation journey shouldn't sell buy only to keep on accumulating without relenting. This is why DCA method is very convenient because it gives you the opportunity to continue buying weekly or monthly regularly irrespective of the price of bitcoin.