It comes down to:
What will you replace your P with?
If it is a much cheaper car (ie: honda, entry level BMW), then it would make sense to sell it.

If it is another P, then you will be paying a lot more per year for a new car then you will for repairs of your "old" car. However, you will have a newer car. - and one wonders if you should have just leased in the first place??