Cuando se ejecutan dos co-rutinas, ¿cómo se detiene la primera co-rutina?

GLOBALS.stableTime = 5;

IEnumerator StableWaittingTime ()
{
        yield return new WaitForSeconds (1f);
        if (GLOBALS.stableTime == 0) {
                GameManager.instance.LevelFaildMethod ();
        } else {
                GameManager.instance.stableWaittingTime.text = GLOBALS.stableTime.ToString ();
                GLOBALS.stableTime--;
                StartCoroutine ("StableWaittingTime");
        }
}