The act of engaging fully in things without worrying about their value is called “playing”.

My advice, if you need a formal way to start playing, would be to join an acting class and then act in some roles.

Being an actor requires you to be able to go all in regardless of how real or fake a thing is. It will allow you to practice decoupling your investment from any evaluation of whether it’s worth it.

Like, if you’re playing an Oompah Loompah, you will act out being very concerned with the running of candy-making machines, despite having zero call for such focus in real life.

This is why we call it “acting”. It’s acting in the sense a robot’s “actuators” are its output. As an actor you cease focus on input and processing, and put all of your focus on your output, your action.

Which is, in a particular way, exactly what your question is asking for.