I accidentally hit a possum tonight and I feel awful. Have you ever done this?

I've hit a couple of squirrels and even a bird on previous occasions. You have no reason to feel guilty for this, because there was really nothing you could have realistically done to prevent this (other than not driving at all). Feeling bad for the animal is one thing, but please don't feel guilty. Moreover, remember that the animal likely did not suffer and never knew its death was coming in the first place. You'll get past this, you did nothing wrong.