When I started AJATT, I was a full time university student, so it wasn't easy, but I tried to immerse as much as possible. I had earphones on in class and while commuting. When I would finish my daily duties, I would go back to living my life in Japanese. I always kept the immersion going at home. I spent all my free time doing something fun in Japanese.
The biggest thing I never did in Japanese was studying programming. Even though you can read books about programming in you target language, I think English is the only language where we have high quality programming resources. All programming languages are essentially based on English.
And of course I would have to pause my immersion when I would hang out with my friends who didn't care about Japanese.