In my opinion, there was nothing to take a lesson, these are the factors affecting the market and any person could not predict this. It is very normal for people to experience financial losses on this scale, but they have the chance to recover these losses in the future by making more proper and wise investments.
I think the direction of the investment is very appropriate if the choice is Bitcoin and ignores new altcoins which are very unimportant to look at. But losses still exist because things are triggered by bad and sluggish markets due to several external factors. An example is the case with Ftx, war, and also unstable economic growth in several countries. So that's what causes the market not to move quickly because some investors are still panicking and are also still afraid to enter the market as a whole as usual.
Lessons for problems like this actually exist, and can be used as a good experience for the future, because with the many bad things that happened in the past year, some people think of taking profits as soon as possible, even if they are small, and enter the market as quickly as possible to buy when they see important assets like Bitcoin are in low price.