You’ll do better on your retest, now you know what the tests about and exactly what the conditions/examiners are like you’ll have more confidence going into it.
I passed C and C+E second time, I think after failing first time I kind of had an ‘oh well, whatever’ attitude for the retakes which actually made me less nervous. I mean you’ve failed before right? So whats the big deal if you do it again. Just practice the reverse some more and believe you’ll do it on the day, because the reverse is your bread and butter. A good reverse and you’ll be confident when you go out on the driving part afterwards.