In fact they don’t account for a changing population at all, as I discovered when I wrote a simple computer simulation to test his model. Thanks to a very basic calculus error, the lines actually show what the cumulative probability would have been if the population had started at the current level and stayed constant. So if we take the orange line at 10 years, instead of telling us the cumulative probability if the population had started at 5000 and fallen to 2500 over time, it gives us the value if the population had started at 2500 and stayed constant. Since this error occurs in equation 1, which the rest of Grimes’s equations are derived from… well, you get the idea.

So it's going into accepting what you can't control, the factors that are out of your hands, and seeing what you can do with what you can control. And learning to be proud of yourself not just for accomplishing what you can, and not beating yourself up for what you can't. Not seeing yourself as a failure, when you haven’t really failed because it’s not something that you could have controlled in the first place. And admiring your ability to withstand a feeling of rejection, and the frustration and the pain, and keep going on towards a more reasonable goal while being a good person. That’s also what’s emphasized so heavily. Figuring out your own values and sticking to them.