Dark Moods

My partner is very prone to negative thinking and dark moods. That’s the thoughts I have about his behavior and the things he says anyway. In the 8 years we’ve been together I’ve always let his moods drag me down. He never ever displays this behavior when other people are around (except maybe his employees). I know his previous partner left him citing his moodiness as one of the main reasons.
Since joining Scholars I’ve gotten much better at controlling what I’m thinking when he behaves this way. I have no desire not to be with him because this is only a small part of who he is.

Unintentional Model:
C: Todd said ………
T: His negativity exhausts me
F: Unloving
A: Withdraw
R: Bad day

As I said I have been getting better at either not reacting to this behavior or feeling annoyed but letting it pass and moving on without letting it completely change my mood.
Can you give me some guidance to continue improving in this area?