I remember when I was a young child we would kneel at the side of our beds and say a prayer we called “Now I lay me down to sleep”. It was a short little thing and it was a regular daily ritual we all did. The prayer was recognizing the end of the day we just lived.
I remember high school graduation, and convocation at university, two more ceremonies that signified the end of one thing opening the way for something new. These too were and are rituals though we may not acknowledge them each by calling them a ritual.
The Jewish tradition of the bar mitzvah makes the end of childhood and the beginning of adulthood when the thirteen-year old boy takes full responsibility for their actions.
The important theme here is that regular daily, weekly, monthly and seasonal rituals are important. They help us get used to the idea that things come to an end and that something new shows up. The end of summer is the beginning of fall. Said another way the death of summer births the fall. As something dies, something new is born.
If it is our desire to be well prepared for the end of our current life rituals that mark common endings and fresh beginnings would be great rituals of practice for our ultimate physical death.
Find personal ways to mark the end of the day, week, or month. Find your way to make more formal the ritual of graduation, the passage of a year, a birthday, and the end of seasons. Doing so mindfully and acknowledging all these mini deaths along with new beginnings will indeed help you prepare mentally, emotionally, physically, and spiritually for your own unavoidable death.