GamingActorTick.scala

var tickCancellable: Option[Cancellable] = None

override def receiveCommand = {
  // ...
  case TickCountdown => game match {
    case rg: RunningGame => handleChanges(rg.tickCountdown())
    case _ =>
      log.warning("Game is not running, cannot update countdown")
      cancelCountdownTick()
  }
}

def scheduleCountdownTick() = {
  val cancellable =
    system.scheduler.schedule(1.second, 1.seconds, self, TickCountdown)
  tickCancellable = Some(cancellable)
}

def cancelCountdownTick() = {
  tickCancellable.foreach(_.cancel())
  tickCancellable = None
}

override def receiveRecover = {
  // ...
  case RecoveryCompleted =>
    if (game.isRunning)
      scheduleCountdownTick()
}