I had this amazing boss. He had 25 years of experience in the sector covered by our software, an ERP. He knew how to be a programmer, a boss, a sales manager, a support person.
I learned most of the best practices from him: do not shout in the office, it makes impossible to work. Don't hide something to your coworkers, nobody was trusting him. Be clear with your clients, his subtle mind tricks pissed off a lot of clients. Your client needs to see an economic advantage in your offers, trying to sell gold priced shit is not a good way to stay in the market. The list could go on and on and on.

I learned what happens when you do everything in the wrong way, and I will never forget.

This one time last year a colleague found out that some data went missing and suggested to recover the data from a backup. When trying to create a new database instance in the Google Cloud Platform (if everything works it's amazing!) it failed.
Not knowing why this happened, I tried to revert that backup to the production database, after creating a backup using the GCP. Needless to say that failed as well, resulting in a corrupted database instance where I couldn't access the created backups anymore.
This all went at around 10pm and the only users of our product are currently in the same timezone and use it from around 7.30AM until 6PM so no one besides our team knew the server was down.
After a long night chatting Google's support team the database was successfully recovered and the only harm done was sleep depravation for me and a colleague.

Apparently there was a bug in the GCP. It was resolved in two hours and the last time a breaking bug was in that piece was more than seventy days earlier.

I did at least learn to create local backups as well, instead of relying on the tools of the same product...

Best: the moment I saw the corrupted database spin up again and not losing my job because of it.