I think this is a personal choice. But in some cases it is simply grammar that decides how I say things. I can say I am anxious or I have anxiety. That works. But I feel like I AM ADD. But I can't say I am ADD, I can only say I have ADD. The other one isn't grammatically correct. I say I am short and I have hazel eyes. That doesn't mean I identify more with how tall I am than I do with eye color.