what is your calling?

I had coffee with a friend and former collegue yesterday. I guess you could say that she is Still my collegue cuz I'm still a nurse. Although my kids think I'm not a nurse anymore because I dont have a job. But anyway.....
Our conversations traveled the normal road of childern and family. But it also touched on us as nurses. We agreed that we felt that we were mediocre to good nurses who do a good job at taking care of patients. I have told myself that I am a good nurse but in the back of my mind there is always the little voice that says "really you think so". And always the fear that I am lying to myself and others and someone will find out my little secret. I know that I am good with the patients and try to bond with them in some way to make their time easier.
We also talked about having a "Calling". We alwasy wanted to Make a Difference in the world; to do something Great, something to be proud of.
I am proud of my children, because for me it is a great accomplishment. It will also show that by the time they reach adulthood, it is proof I didnt kill them.
I have thought about my Calling. What am I supposed to do with the time God has given me? Besides my children, I have done nothing that even relates to having a Calling. I am a nurse, but not all of the time. I am person who plays with yarn and creates beautiful things. What is a calling really??