That must of been hard...really, really, really hard to do. As a car guy, I miss every car I've ever owned, even if was a POS (didn't we all have something like that?). For me, they become family members not just transportation. I've tried to convince myself "it's the right thing to do", and even if it is, it still just doesn't feel right. The last car I sold (traded in), I actually left a note (in a hidden location) for the future owner describing the experiences we had with the car; yes I know that's weird, but I wanted to let someone know we cared for the car and hoped they would as well.
In your situation, as you sold yourself, I hope that (if you wanted) you can keep in touch with the new owner. Perhaps they would also share experiences and maybe you would end up with a new friend to replace the one you just lost, or at least you could take solace in the fact that the car will being going to someone who will drive it and end up with a second chance at life.
Best wishes on your new purchase, or should I say congratulations on your expectant new child?