So what I'm understanding is that you felt displaced?
Your feelings are definitely 100% valid.
I feel like I can relate.
When my dad remarried I kept trying to talk sense into him and he wouldn't listen, now he's in a situation where he is truly miserable..
I hope for your dad it's different and he found a good companion for life.
At any rate, you are his daughter. You know him better than nearly anyone.
I feel like radical acceptance is like "Okay, it is what it is, and I can choose whether or not I want to be a part of it"

I feel like we should treasure our feelings and never undervalue them.. I'm sure you're smart and it sounds like your dad rushed into things? I could be wrong. I felt like my dad was in such a rush.

Not to mention bros before hoes man. IF (God forbid) it doesn't work out, who will be there? YOU.
http://www.positivelypositive.com/20...ke-a-bad-mood/

I don't think this has anything to do with you not being happy for him.