I find you can almost always replace “but” with “and” in situations like those and end up more heard by the other side.
I understand the urge to feel heard AND whenever we bring something that may contrast we risk the disagreement connotation that “but” carries to trigger the recipient’s defensive reaction (even if unconsciously)
First rule of relationships: adhere to the first rule of improv!
Depending on the relationship involved, asking the person why they think I behaved as I did often helps. Sometimes the reason they think I did what I did is more correct than what I would have put after but or and. And sometimes the answer they give shows they are modeling my motivations completely incorrectly.