Thanks for introducing this concept! Building on this, I find what works for me is actively helping someone else achieve success. Giving feedback on their work, for example, cheering them on, or attending a celebration of their achievement. I feel like I've "invested" in them and can be proud of them because I put in some work too. I don't own their work, obviously, but I do think I have some share of it. This is a win-win: I help you and I get to feel proud of you too :)