The Sith saw no need to take on only young disciples, though they often did. Sometimes the training went smoother with disciples who had lived long enough to grow disillusioned or angry or vengeful. The Jedi, by contrast, were shackled by compassion. Their penchant for showing mercy, for granting forgiveness, for heeding the dictates of conscience, prevented them from giving themselves over to the dark side. From becoming as a force of nature itself, paranormally strong and quick, capable of conjuring Sith lightning, of exteriorizing rage, all without the need for the magic hand passes the Jedi were so fond of employing.