14 flights really isn't very many, you had changed glider types and you were nervous about flying with a different instructor, so lots of things working subetly against you.
Learning any new skill is very rarely a straight progression, St Vitus dance is far more common especially with older learners.
It all sounds very normal to me, and I'm crossing my fingers the weather improves so you can go back and have a good day.
BTW if you never ever get nervous I'd worry about that much, much more.