I came across this term when listening to a talk on stoicism which is a Greek and Roman philosophy arising in the 3rd century, BC. It is a philosophy of life that maximizes non-reactivity enhancing positive emotions while reducing negative emotions. It is very Buddhist in flavor.
Prospective retrospection is experiencing something now while contemplating how this event will take on a different meaning in the future. I have been doing this for years. Especially with people I love. I will be hanging with someone and contemplate their death and the truth that they are no longer alive. It helps me become more present to this person. To love them more and even overlook attributes that they may possess that aren’t favorable to my peace of mind. This is a very powerful practice.
I also will do with places like my home. I will stop and look around and remind myself that someday I will not live in my home. I feel into this feeling. Appreciation and gratitude always arises. It helps me feel a deeper connection to the present moment and appreciation for what I have.