Narrowing my niche

I had formally worked as an in-house corporate coach in a large company. I’m getting ready to leave the corporate world and establish my own coaching practice. I want to combine the tactical knowledge I have gained through experience with the skills I’m learning in the Life Coach School. My “value proposition” is that if you are not where you want to be in your career, the problem is not your boss, your skills, the competition, the problem is inside your head, what you THINK. I’d like to help people change their thinking, and then help them with a new career, a pivot career, advancing to the next level, etc. I don’t know how to articulate it, and I’m worried that it’s just too broad.