Job interview with doubts

A position above my actual level opened up in my company and I applied as I would like very much to move to that function. I am actually now on the short list but my boss told me that there are other external candidates with much more experience than me in that field. He said that decision will not be easy for him.
On the other hand, I am really terrified by getting this position as I am going out of my comfort zone. Also, I am scared that if I get it, I will have much more difficulty in taking care of my family (activities after school etc.) as the job will be more demanding.
I am trying very hard to manage my thoughts. I understand that there is no right or wrong decisions, but how can I appear convincing when I am in interviews if I have all those thoughts in the background?
Thank you for your help:)