I don't know if it is jealousy or envy but it is hard to watch couples together. For me this is especially true if the couples are older and appear to have spent many years together.
I see these couples at restaurants, shopping, even at my gym. They may be happily married, they may not be. I have no idea. But you can see that they function as a team. In most cases a well oiled machine. They don't have to talk they know the plan. Where to meet. How long he can tolerate shopping. When she is ready to go home. When one isn't feeling well.
Lane and I had a some rules we lived by. When we made arrangements to meet somewhere don't wonder off even if the other person is late. When visiting family never park the car in the driveway. (easier to leave when no one is behind you) Watch for non verbal cues that say stuff like "Bored. Let's go home." Or, "Put the drink down. You've had enough."
I do get jealous when I see couples doing exactly what Lane and I did. Living life with an understanding that you and your spouse can communicate with just a look or a touch. Having rules that only you two share. Being married.
What makes you jealous?