Don't worry about it. The hobbies to watch out for are the ones that use all the same skills as your startup idea. I.e. the other programming projects that wil

Don't worry about it. The hobbies to watch out for are the ones that use all the same skills as your startup idea. I.e. the other programming projects that will drain your focus. You're not going to accidentally spend 8 hours playing piano instead. Also, playing piano will help you maintain your focus.