Yes, this is a good tactic, sell on growth if there is a fall, buy more. With this strategy, you are less at risk. But this tactic that you describe is not like trading it is most likely an investment. Since when traders see that the market is not going in their direction they close the deal at a minimal loss. And according to your strategy, people have been waiting since 2017. this is not a trade but an investment.
Good observation you have there mate. For all we know we have been buying and buying when the coin or token is at its lowest - at a certain point in time. What I mean is if the coin is low that day then we buy more coins. If you are not satisfied with the performance of the coin then you wait until you get the selling price you want and as you say it becomes an investment. But what I like to know with our fellows here what would be the best day strategy that you can implement to ensure that you can get more profit on that day?