Standing up for myself

Hi coaches,

I already wrote yesterday but I think more insight would be very useful.

Soon I will have to defend my interests against my business partner. What I realize is I feel dread thinking about doing it because I never put my interest before the ones of the person in front of me. Never. I guess I do this to avoid getting into conflict. Now that I find myself in the situation where I really want to defend my interest otherwise I will lose too much, I can see how I dislike putting myself in a situation that will probably end up in conflict. Usually I settle without negotiating or defending myself and my interest. I think now is the time to face that fear because I am tired of letting people get what they want.
The thing is my business partner also was my friend for 10 years and during those 10 years, I never once got the last word in an argument. He always screamed harder to make sure I would stop contradicting him. And I did. We haven’t been in each other’s lives for 2 years now and I know I’ve changed but still I am not sure I can hold my ground in front of him. I never could before…

So basically I’m determined to stand up to him this time but I’m worried he will get the best of me as he used to do before, by yelling and trying to intimidate me. How do I deal with that doubt? I can’t seem to make myself believe that I can stand up to him..

Thank you for your insight