Tips to help stop spiraling?

I have Generalized Anxiety Disorder, and as such, whenever anything bad happens, I often tend to freak myself out about it and convince myself that something horrible will inevitably happen if I don't fix it. The most frequent example of this includes arguments/fights with friends and family. I had a friend who was manipulative, and would start arguments over the stupidest things; these arguments were almost never my fault. But I would spiral so badly that I would apologize to her, even when I really shouldn't have, so that my mind would stop it with all of the what-ifs.

Yesterday, I had a fight with my dad. Truthfully, it was a fight caused by his actions, and not mine, yet he still blamed me. I had my mom come and get me so that I wouldn't have to be there, and I positively refuse to apologize. It's not my fault that he didn't tell me that he almost sold our house without telling me while I was away at college.

But now, my mind won't quiet down with the what-ifs. As of right now, in my mind, my dad is going to vent to my Nana, who will get super frustrated by it, and her heart won't be able to handle the stress, and she'll have a heart attack, and maybe die, and it'll be all my fault because I didn't suck it up and apologize.

Which, again, I'm not going to do, regardless off how crazy I drive myself.

I've never spiraled this badly before, and I'm going insane trying to cope.
Does anyone know anything that I can do to calm down my thoughts?

Thank you!

I like the Ativan route personally. I can’t focus on things like meditating or breathing or thinking if I’m in a tailspin.