This is a trap I see often, especially with celebrities (movie stars, musicians, etc.) who don't have to work anymore thanks to financial success, or people who come into money suddenly (inheritance, trust fund, lottery, etc.). That's also a big part of the reason I don't ever want to retire...left to my own devices, I do not do well, and "lose focus" just like your friend did. Having some kind of cause to pursue (whether it's college, or a steady paycheck, or whatever) can be really great for your life.
Personally, I need to be plugged into a social community of workers to stay motivated. As introverted as I am IRL, I also recognize the benefits that working around other people brings. There are definitely people who have enough drive & willpower to stay self-motivated in an isolation bubble working at home or living in retirement, but it took me many years to accept that I am not one of them. That's actually a big part of the reason why I post on ATOT, reddit, etc. - it at least keeps me plugged in, to some measure, to things & to communities I'm interested in. It keeps that discussion going mentally, and in turn keeps the motivation flowing, because it kind of forces them to stay living, breathing things in your life, instead of just a memory that is easy to let slip & forget about.