It is very true in a physical sense. "Use it" results in neural pathways being formed. What happens when you dont use them?
https://www.sciencedirect.com/science/article/abs/pii/S01602...
https://www.sciencedirect.com/science/article/abs/pii/S01602...
Likewise for physical exercise - it took me a year to hit 100kg squat when I started getting into shape 10 years ago. I haven't been very physically active for years but I'd hit 100x5 in a month of starting gym again.