There are a few different things that can help overcome the fear of death. Mediating about death, such as gazing at a tombstone in a cemetery or visualizing your body rotting away before you can actually help with accepting death. Evoking and working with death deities can help as well. A more extreme method that can also be helpful is to perform a ritualistic “death” such as one I wrote here. While the purpose in the post was more geared for those who desired an ending of their own suffering to open the door for a better life instead of physical death, the purpose can be shifted to overcome the fear of dying.
If you feel like you want to try any of these but feel you are psyching yourself before starting, look up a concept called “death denial”. It is not a pretty road to go down and has been a classical theme in cinema you have probably seen. (For example, the origins of Darth Vader in Star Wars, as Anakin was a classic example of one who was in death denial).