Hm. Generally, I try to validate feelings. Logic and emotion, for me, don't mix well. It's okay if somebody feels jealous. It happens. Looking at why might be good though, if it's something that really bothers them. Letting someone examine their feelings (or me examining mine, which has definitely happened) while saying it's okay to have them usually has a pretty positive end result, without setting up an argument for "telling yourself not to feel ___." Because there's no expectation that each person will tell themselves what to feel about things, just that they'll be dealt with and processed as they come up, good an bad.
“Great things are not accomplished by those who yield to trends and fads and popular opinion.” -Kerouac
I'm R (male), I live with D (male) and L (female) and L's two kids.