Have to say "I am going to do..."

He was driving to take me back home. I keep quiet unusual.
He ask: “What are you thinking?”.
Answered him: ”Do you think that i should change my major is better?"
"You can do whatever you want, but can tell me why? What major do you prefer?", "Do you think you will do new major well?" He asked me the rapid-fire questions so that i couldn't take time to answer.
"Maybe finance. I don’t know, but Marketing seems not for me." I continued, "I do like Marketing, but I am not sure I can do it well when I get old and get married..."
Dropped my talk, he said: "Are you sure that you like number? How you know you can't do it well?"
"Number? not really, but I know that the older I am, the less my creative is, I think, I might not do it better than who are younger than me when I get old" I said.
"You won’t be a staff, of course, Sarah. You are a manager at that time. You will ask somebody else work for you. You might have less creative, but you have much knowledge and experience. Why you don’t think like that?” He spoke.
I was tedious and said:”Uhm.. yah.. I am just afraid that I could not…”. Dropped my say, she looked at me with his wide-open eyes, seriously; “Don’t say that again. You have to say – I am going to do that”
I felt scary him as if I just had done something wrong with him. I just kept quiet and listened to his talk as if I had been a child paying attention at the parents saying….
He continued, “If you think that way, you will never do what you even want to do. You showed me no reason for your thinking, and didn’t persuade me of your new choice. Once again, DON’T SAY “I am afraid doing something. I WANT YOU TO SAY “ I am going to do something”. If you think this way, you are very sure to do that.”
And, continuing with “ Now, answer me what do you think about learning driving? I know you scare speed, answer me.”
“Yes, after finishing my school on summer, I will”, answered him immediately because that was my plan.
“Yes, right. You scare speed and car, but you are going to learn how to drive”….and, you know, there are a lot of thing you have to say “ I am going to do all” Be strong, smart and brave. “.
A few minutes later, he kept quiet while i was thinking... He said, " answer me when i make a decision."
“I am going to do….” has been in my mind. You know, I talk with myself about going to do something before planning to do things, and I feel that I get much motive power to do them. I have to talk about my choice tomorrow with him. Can you get what i could say?