I have always said that buying in the dip is the best thing to do, especially for BTC, however there are times when you have to take into account the capacity that people have in your pocket, it is very easy to say that you are going to buy in the dip, but if there is not enough money? And if you buy and keep going down, the logic indicates that you should keep buying, but if there is no more? so I prefer to set a buy price level and if the price goes down even more, I sit still, I do nothing else but Hodl until I can the price go up and make a profit.
You're right and buying the dip is most effective if you have done the selling at tip part because otherwise, you will run out of funds very quickly. It's perfectly fine to keep buying more for whales or people who generate income outside the trading but for common traders we have to be sharp and selling at the tip is equally if not more important than buying the dips.
Trading is easy if you just do what's the right thing to do at the right moment. Some people are hyped and buy the tip and sell the dip which is what is causing 50% of the traders to lose money. They panic when price drops and get hyped too quickly when price is rising.