Would you bother preparing something to help prove your reincarnation, or would you simply take advantage of whatever you retained (and prepared for yourself) from your past life?
How might you use this ability to help yourself and others?
Edit:
To clarify, suppose you have some vague memory of your past life in your reincarnated self that helps you along and allows you to take advantage of whatever your past self prepared for you.
On a related note, no one ever talks about the movie Chances Are where Robert Downey Jr gets reincarnated and falls in love with his daughter. Don’t worry, it’s not weird because his (ex?) wife approves.
Do you suppose stories like this are sometimes trying to emulate Oedipus Rex but missing part of the point?