it's funny that some persons will wait for moments when they see bitcoin price going up before the thought to invest in bitcoin comes to there mind and like you rightly pointed out, bitcoin price can go up and then up, up and then down, down and then down and so on. so you can't just predict that because it is going up now , this is absolutely the time to invest into bitcoin and when you see the price going down you retreat from your plan on making the investment. It means that if you even successfully make the investment, you can't hodl your bitcoin because in the event of any fluctuation in price, you will let go of your investment.
Real investors sees the prospect of bitcoin and invest a certain amount and leave it for quality amount of time while he monitor the price without getting seriously moved by any fluctuations in price that comes along the way.
When bitcoin prices are high, anxiety and fear of missing out usually lead some people to consider investing in the bitcoin. They are motivated by the belief that if they invest now while bitcoin is rising, it will continue to increase and they will profit from it without considering the possibility that the crypto market could quickly go from being sweet to bad.
Instead of focusing solely on the current price, whether it is high or low, every crypto investor should set a long-term price target that will help them determine when to purchase and when to sell for a profit.