Leaving soon

I'm 19 going to Job corps on the 14th one state away from me and this is the first time I've ever done anything by myself I don't know the first thing about living by myself but im ready to leave. The problem is I have some people doubting me and saying I'm going to quit and it's got me thinking it's going to be really hard I know it's going to take some time to get use to but it's hard when you have people talking down about a big step in you're life. What are some things that motivated you guys and made you less nervous or scared when you where about to leave or when you first got there.