Here's a quote from the movie 'Kung Fu Panda':
Quit. Don't quit. Noodles. Don't noodles. You are too concerned with what was and what will be. There's a saying: "Yesterday is history, tomorrow is a mystery, but today is a gift. That is why it is called the "present".
Here, is the what an interrogative word or a relative pronoun?
In other words, what does the sentence mean?
(1) You are too concerned with the questions of what was and what will be.
(2) You are too concerned with something that was and something that will be.