Whether or not we have free will and whether this whole existence is pre-calculated, I'm going to go all meta-Pascal's wager on it and suggest that we try to act like we do have free will and try not to think about it.
Maybe I was always going to come to that conclusion. Doesn't matter.
Maybe this makes about as much sense as Wile E. Coyote staying in the air until he actually realises he has run off a cliff. Doesn't matter.
Be the Road-Runner able to run into a painting of a tunnel as if it is real and remain as happy as possible about it.