Why do I

Lose all interest in doing my hobbies the moment doing them doesn't mean procrastinating another task.

I was all week studying for exams while thinking about starting a new Minecraft world to play, I made the world and played for about an hour before going back to studying.

I took the exam today, went home thought about playing the world, opened Minecraft and just left to do something else.

Whyyy!?!?!

Am I stupid? I spent all week thinking about having fun playing mc but the moment I can relax doing it knowing I have no chores or responsibilities to take care off playing the game becomes the object of my procrastination. Why am I procrastinating fun?;why does my brain process playing my favorite game as a chore?