1. Your private library should be quite small. If you find that you have 100+ books, that you do not read on a constant and regular basis, you are either wasting your money or signalling pseudointellectualism. The reason is that books are expensive (relative to their market price) to store (you need space for a shelf) , and a back-of-the-envelope calculation returns that you probably should not keep a book that you are unlikely to ever read again. Given that you have limited reading time, you can pretty easily estimate your maximum library size from there. I read a lot of books but only keep roughly 15 or so permanently.

2. Adults learn new sports quicker than children and teenagers do. Most people assume that children learn everything faster, and that this holds true for sports. After all, most professional athletes start out as kids. However, adults are often better at knowing how to learn stuff quickly and are usually more motivated. I learned multiple new sports as an adult and as a kid and progressed faster as an adult. I also became better at these sports faster than other children. I am not aware of any evidence that suggests that children learn faster than adults. Professional athletes started out as children because they maximised their time spent training a sport. It does not mean that they learned the most in their childhood.

3. Most people do not filter the air that they breathe, but they should. The negative health effects of air pollution are massive and can be reduced greatly by setting up an indoor air filter. We bought a 100$ fan + 30$ HEPA filter (that also filters viruses and bacteria) for our apartment. Studies find that such equipment increases life expectancy by as much as 6 months! This is “equivalent” to not smoking 1 cigarette per day. Any decrease in infectious disease (such as COVID) is bonus on top.

4. You should be as strict about your daily routines as athletes are because they care about achieving their goals. Not being as strict about your daily routines could mean that you are not trying to achieve your goals. 

5. You probably should not pursue a degree immediately after finishing school. If you are like most 18-year-olds (including me at the time), you are extremely inexperienced at pretty much anything. That is not only okay, it is quite refreshing. Think of it this way: If you had a friend that was not sure what to do with their life, would you recommend to that person to do the same thing for 3 years straight? I would not. Rather, I would recommend to take some time to figure out what you want to do, and to find out as quickly as possible. The most practical version of this seems to me to do a lot of things that are by definition short-term, such as traveling, dabbling in different university programs, talk to others,  work as a student assistant in many different roles etc. On a deeper level, I think that this reflects societal friction due to change: I talked at length with my grandparents about their careers; they just picked something and went with it. They had to, because they did not have many opportunities, and every job was better than living in poverty. This is different now. Many people now have the financial freedom to pause their jobs for a month or 12, and to reconsider what they want to do.

6. If you claim to be interested in the greater good, you should give away substantial portions of your money.