My brain is fighting it

I’m part of a program that is teaching me new things – mainly about mindset as well – and notice my brain is fighting the work so hard. I’ve wanted to be in this program FOREVER but here I am, in it, and my brain is saying “No, that’s not true. That’s not going to work.” and things like that. I feel like I have to battle my mind here, so that I go all in on the program.

Could you please help me with:
1. What to do about it? I’m tired of fighting my own brain to get rid of those thoughts.
2. Explain why my brain is doing this? It’s something I wanted so it could help me, but now that I’m here it’s rejecting it