Why are my conditional checks are failing and firing a function?

I am using react-query hooks, my goal is to send the updated state to the database and receive the updated state as well.

My object is a workout diary that displays exercies on each given day:

{
        name: "my workout diary",
        currentDay: 0,
        days: [
            {dayName: "monday", exercises: {...}},
            {dayName: "day 2", exercises: {...}},
            {dayName: "rest day", exercises: {...}}
        ]
    }

The number in currentDay field indicates what day currently is being rendered on the screen from days array.

I have 2 buttons that move day back or forward using useMutation hook:

    const query = useFirestoreDocument([...],ref);
    const mutation = useFirestoreDocumentMutation(
        ref,
        { merge: true },
        {
          onSuccess() {
            queryClient.invalidateQueries([...]);
          },
        }
      );
      const workoutplan = query.data?.data();

      const moveDayBack = () => {
        if (workoutplan && !mutation.isLoading) {
          workoutplan.currentDay > 0 &&
            mutation.mutate({
              currentDay: increment(-1),
            });
        }
      };

Everything works just the way I want to if I do it slowly, but if I spam movedayback function fails the conditional check and sends the -1 to the server then goes back to 0, but that causes fatal error, because negative array index will return undefined.

Why are my conditional checks failing and how do I prevent that?