The first is also referred to as the fast fail model. Try 100 things, quit the bottom 98 as fast as possible so you can do the best 2 effectively. The faster you can quit the less successful ones, the more options you can try out and the more likely you are to find the best ones. But it is hard because we have trouble letting go of our ideas. When you start out thinking an idea might be a good one, we get cognitive dissonance admitting it is not. We also suffer from confirmation bias (among others) when evaluating the idea, so we may think it is better than it really is. Developing the skill of failing fast is very useful, especially in areas such as innovation and kaizen.
They also apply the idea of quitting to career development. Think of the opportunity costs of continuing to work at a job or in an industry that you don't like. Sunk cost fallacy tells us that we focus on all the years and time we have already wasted in this field so we can't switch now. But it's called a fallacy for a reason. It is never too late. For young IEs out there, think about the industry where you work, the experience you are getting, and the expertise you are building. Is this what you want to do? If not, the sooner you quit the sooner you can get on a path to what you do want. And the sooner you do it, the easier it is because you have less cognitive dissonance and less sunk cost bias. Is it too late if you are 50 and dissatisfied with your career? Nope!! Even then, you can apply what you have learned in one area to another that might be more meaningful to you. There were lots of great examples on the radio/podcast special (no IEs of course :-D).
Quitting is even harder when the thing you need to quit is part of your identity and self-image. Musicians who have tried to build their rock band career, actors who have been trying to build an acting career, minor league baseball players after 10 years in the minors, etc. Rock/acting/baseball isn't just what they do, it's who they are. We can have similar situations in IE. Perhaps all your life, even as a kid, you were a "car guy." You were working on cars with your dad when you were 5 years old. Everyone knew you would get a job in the car industry. IE was just the particular path you chose. But now you are 45 and realize it isn't meaningful any more. Admitting this to yourself (and to everyone you have known your whole life) is tough. Many people can't do it. Some go to therapy to develop the strength to do it.
But do it, whatever it takes. You spend more time at work than doing anything else. It should be something that makes you feel good at the end of the day. When you love what you do, you don't have to "work" a day in your life. And this happiness transfers to other parts of your life. You become a better spouse, parent, friend, and more.