As previously mentioned, Clara has managed to fit in more than just about every other previous companion in Doctor Who history during her respective stint in the TARDIS. While there's a never ending plethora of stories to be told within the Whoniverse, what else can she possibly accomplish for herself? She's saved the Doctor more times than anyone else, helped him through a regeneration, went back to holding a semi-normal job and, as of Series 8, she's even been the Doctor (as part of a ploy to outwit the Cybermen) and subsequently taken pride of place in the opening credits. The poor girl needs a break and with the upcoming Christmas episode being a series finale of its own (it's technically a standalone episode but for all intents and purposes, it acts as a finale), now is as good a time as ever for Clara to bid adieu to the TARDIS and, this time, for it to be for good.