It sometimes happens to me. I'm thirty years old and I see some contemporary friends who have a good life (sometimes according to what I see in social media). I feel happy for them but at the same time, I'm worried about it because I haven't reached some goals that they did. It's kind of pressure.
I think it's not ok worrying about that because the time of reach goals is different for each people, and as you said, the concept of happiness is relative for each person. So, I try to be to be calm and keep working for reach my goals.