As much as I love Twelve and Clara and miss them being together, can you imagine what would have happened if they stayed together? What the Doctor could have done for Clara? The stuff he would be willing to do?
Well, let’s start with a beautiful wedding ceremony… then a tiny baby hybrid and maybe another … crazy family life on the TARDIS, the awkwardness of having to explain Time Travel to the earth family and why the grandkids were 7 last time they saw them and now they’re 5… yes, I do think about it. All the time.