People like this are usually people who have never been in 1 bitcoin cycle or about 4 years with bitcoin, the average new person who does and has such a nature.
When prices drop fear, when prices rise FOMO, until whenever people like this will not get a decent profit from bitcoin, but I think they will learn from their mistakes if they already have 1 cycle experience with bitcoin, more or less will understand the bearish and bullish of bitcoin and can have a mental addition to how to invest in bitcoin.
To implement this, a good financial strategy is needed, such as one of which we must have cash to increase the accumulation of bitcoin when the price drops.
That's a typical behavior of newbies in the industry with no interest to invest or to do their research. One doesn't need to told of when to sell or to buy as long as they've taken time to check bitcoin price history but they prefer to be instructed of what to do. One thing to note is that people like this are not ready for the good or bad of the market, they are only interested in making quick money in a short time.
There's no bad time to buy bitcoin as long as one is ready to hold for a long time but buying at dip is more advantageous and profitable but time for selling is absolutely your decision to take if you think you are satisfied with the profit. You don't have to invest in bitcoins based on people opinion, engage in personal research to know what is good for you.