Yes, it is very normal to be nervous! You are having real surgery and one that gives you no physical benefit so it is different than all other types of surgery. Do you have a good support group? Perhaps, you can get a donor buddy from your hospital to help you along. I found it very comforting to talk to other donors, especially donors who were struggling with this surgery. Try to do things this week and next that are calming for you. Walks, exercise, yoga, massages, journal your thoughts, maybe work on a scrap book of this whole event and then add new photos and things as you continue. Make sure all your questions are answered, have someone stay with you at the hospital and then maybe at home for a few days after you are discharged. Each day will get a little bit better. It takes a few weeks for you to feel back to normal. Allow yourself to be a patient even if your mom has been the one sick with kidney disease. Most likely she will feel much better when she has a working kidney and you will feel wiped out. Let your body heal.
Where are you donating? If you post on the regular forum someone else may have donated in the same place and can give you a little encouragement.
Thoughts and prayers to both you and your mom for a full and speedy recovery.