I currently work every day on a codebase that is >95% not mine and changing, and its very fun. Some days I'm just as productive as on my own projects, sometimes

I currently work every day on a codebase that is >95% not mine and changing, and its very fun. Some days I'm just as productive as on my own projects, sometimes 1% of that. I think there is great value in letting yourself enter this hacker flow state on other people's code - its new and exciting.