Over the years many people has ended up losing their bitcoin that is worth billions because of exchanges being hacked, scam activities, forgetting passwords, security practices that are very poor and errors made by people holding bitcoin.
The best effect from "lessons" is achieved only when the user has learned this lesson through personal experience.

lesson learnt:
The lesson learnt in this is that once a third party or person is controlling your private keys they actually controls your bitcoin.
Convenience often comes at the cost of sovereignty, know this and no peace.
In some cases, handing over control of one's bitcoins to others is a better solution than having the user securely store these assets themselves, as they can be so irresponsible and careless.
lesson learnt:
It is true that self custody provides or gives us freedom but let’s not also forget that it also comes with responsibility.
Having a good backup strategy to our wallet is as important as owning a bitcoin.
This is not freedom, but a burden of responsibility.
lesson learnt:
When the opportunity is too good to be true avoid it.
There's just no need to chase easy money.
lesson learnt:
Always verify addresses very well before sending and you can also consider sending a very small amount for testing before transferring large amount.
This requires time, i.e., not to make transactions when there is a shortage of time for this process.
lesson learnt:
A lack of conviction about bitcoin can be just as costly as poor security.
This isn't a lack of conviction, but rather an investment strategy. That is, there should be a bitcoin sales plan and no selling until that point is reached.