My dirty little secret: I'm looking forward to having my own apartment so that I can practice (violin, piano hopefully, marimba, kazoo, etc.) at all hours of the day. Oh, yeah. I try not to do that now in order to avoid waking up my ridiculously hard working good lady mother.
I'm carrying on my violin on the plane as my one "personal" item. Helpful hints and advice have included wrapping the instrument up in a bag to prevent cracking due to loss of humidity, and remembering to remove extra strings from the case, lest they be confiscated as the dangerous weapons that they so clearly are...
My college violin teacher tells a story about practicing his violin in the student apartments one afternoon (quietly and with the mute on). Some old guy starts banging on his door and yelling at him to stop making such a racket. My teacher is baffled as he can't see how he could possibly be making that much noise. The next day, that same old guy comes knocking on his door again and apologizes saying "I'm very sorry, it wasn't you."
I'm prepared to feign innocence if questioned about a "racket". Complete deniability is essential.