Having your life story prepared when you have the opportunity to do it, has three main advantages.
The first, logically, is that you get to have your life summarised and recorded in the way you would like to be remembered, and can be used as the basis for a "This is Your Life" style ceremony to mark a particular age achievement.
Then, it provides a history that can be passed on to your descendants.
Finally, at the time of your death, when your loved ones are likely to be in a state of dismay or despair, a record of your life and wishes for your funeral will help them to work with the celebrant that you, or they, choose - to ensure that your final ceremony is a positive one.
I will work with you to write a summary of your life story in the way that you would like it to be recorded.