I spent my career in computers, and computers were my hobby and passion too... I was living and breathing the stuff 24X7.
When I quit, I finally had enough and dropped it entirely... and don't miss it one bit. My retirement passion is photography. I spent a year building an addition on the house which serves as a studio, and I can make a little money shooting headshots, boudoir and things like that. I also shoot models and sell online photo books via Kindle and Nook. My wife likes it because travel photography is fun too and she's happy to travel anywhere. I also make a little income selling stock photos from travel... Costa Rica, Argentina, etc. Most importantly, its fun!
I'm using a Raspberry pi 3 to program a TI MSP430 for a home project right now. I never got enough of the parts of this I like at work and I don't miss at all the drudgery of trying to forecast when I would complete a project.
The parts of the project I understand take very little time and the parts I don't understand will take however long they take. I'm "paying" the development bills now and I really don't care how long it takes.
Digital photography is all about computers and digital technical grimble. Fun though.