All the senior devs I've worked with who seemed truly happy at work were that way because they spent plenty of time with their family, volunteering, and just do

All the senior devs I've worked with who seemed truly happy at work were that way because they spent plenty of time with their family, volunteering, and just doing stuff outside of work that was meaningful to them. None of them poured everything they had in their job, tying it with their identity. People in that latter category tended to be more brilliant in general (for example a problem comes up and they immediately know of 3 different ways to solve it, half a day later they tested all 3 for that particular problem, half a day later a first implementation is up and running, while it'd take most other people a full week to reach the first step), but they seemed to have way more up and downs with their mood and happiness and general. Obviously this is a generalization from my ~10 years or so in professional dev environments. As a senior dev who tends to identify more with the second category in terms of happiness fluctuations, I've been trying to be more like people I've known in the first category.