I certainly know how you feel.  Seems to me that time was the only thing that cured that for me.  Here is one thing that helped me alittle, I found a stylist in the salon who was very confident in her work, weather it deserved so or not, some people are just more confident than others, and I listened to how she spoke to her clients.  Listened to her wording, its ok to copy them for a while until you can get your own grove down!  It will also come when you have more of an establishede clientele and you just feel more comfortable with people.  Good Luck

Tanglesgirl

R 

here's a phrase i heard Geno Stampora say in a Brocato class back when i first started in the 90's:
  if there's anything you don't like about what we've done with your hair today, PLEASE tell me-if not, please tell everyone else!!!

this way you're covering the outcome in two ways-ensuring they like it as well as asking for referrals because of it.

Definetly learn to calm down. If you keep asking your client if he/she is happy, that is a red flag you have no idea what your doing. Even if your not comfortable, act as if you have been doing it for 100 years. A simple how's that? or good?...will do. I also found that a quick summery of the service after you have finished helps as well. This will let the client know that you are confidant with your own style.

I really believe in practice . The more you practice your skills the more confident you will become. the listening to other more conf. stylists is great advice also.  Believe me if the client hates it most will tell you, you will see it on their face,  but also remember you can't please everyone all the time. After all if we were perfect we would be goddeses and no one treats me like a goddess so I must not be perfect....If you did the best job you can and learn in the process it will come. while your still nerved just try to curb how much you say and how you say it.