Every time he opens his mouth except maybe if he is discussing logistics. Any complaint, whine, stupid comment, emotional expression, whatever. Just validate.
Photo nailed it with her unique style! Example:
H: We have no choice but to split up. Overcom: I understand why you feel that way, but I feel very differently.
H: I can't do anything right. Overcom: What makes you say that? H: I mess up everything I do. Overcome: I understand why you may feel that way, but I can think of lots of things you've right.
I do a lot of understanding H's feelings, and will either redirect, or agree to disagree.
