grief before grieving

does anyone else struggle with pre-gaming grief in their life? like I am lucky to have people that mean a lot to me that are currently present in my life and are showing no signs of leaving, yet I've already cried and worried over their deaths, personal problems, or seperations from me. when I am at a good point I can't help but wonder how long it will last instead of enjoying it in the moment, and I constantly remind myself that I never feel this happy so it must be fake. I hate doing it, but at the same time it feels comforting, like maybe I'll be more ready when it comes? but then when I experience real loss I often just feel a void.