Regardless how experienced or educated you are you will still make financial mistakes, some of them humdingers. Personal finance blogs and media outlets frequently share basis financial mistakes to avoid: spend less than you earn, invest in index funds, avoid debt and so forth. All this is good advice, but it goes a lot deeper than this.
The demographic reading this blog does the things necessary to retire early. The same demographic believes in a side hustle to retire even earlier or to fill time once work becomes an elective. These facts make hobby rules an important consideration. The tax law has a massive loophole few use.
Accountants in the room will understand what I say next. A client walks in the door and his hobby finally turned a few dollars of revenue. No worries, the client says, I can lose money in my business for three years before I have to shut it down and start over. The client actually thinks there is a rule saying you must make a profit 2 out of every five years. By this yardstick, Tesla, a publicly traded company, would have to shut down. (Tesla has a decade of loses as I write this.)