I don't think we can (or should) manufacture how we feel? Feelings are part of our makeup to help us maneuver through the world, not something we pick up and use as we would like, to shape the world. The world has a shape (your wife is going to Roswell with your BIL) and we have a response to that (that's great, now I will be alone and able to sleep in and eat what I want, not have to worry about someone else, etc.; or, I wish I were going; or, I wish BIL were not involved) but it makes no sense to me to want to script our response. Our response is.

But, how we feel is not the end of it. We don't have to say, (talking being an "action") "I hate you, you get to go to Roswell and I don't and I wanted to go" (I had that when my husband and stepson went to the beach for a week but I had just started a new job the week before so could not take off), we can decide to recognize that we wish we could go and how we'd feel great if we could so extrapolate that the other person feeling great that they are going (or upset because they want us to go and we can't), we can "understand" their feelings, even if their circumstances are not ours at the moment. It does not help or hurt us to recognize our feelings and recognize the other person's feelings and realize we are in different situations so the feelings differ.

I temper being "happy" for the other person. That's not my job, being happy "for" someone else; they have their own feelings they are responsible for expressing! I can say, "Gee, I wish I could go too, I'm jealous" without sounding snarky or self-pitying?

Presumably we are involved in our own lives so other people's lives, where they are not connected to ours, we don't have "time" for? I had just started a job and was not into vacation, had the excitement/duty of a new job and getting to know it and finally getting income and doing what I was doing in my own life. If we are too busy standing at the fence all the time looking over, we're going to miss our own lives and the need to mow the lawn on our own side. The more we compare instead of do, the more our side of the fence gets to looking crappy because we're not caring for it.