The short answer to how we become comfortable with death is honoring those that have died. Though art, music, writing, film or simply showing up every day and being present.
The day of the dead is celebrated in many cultures.They have created rituals and celebrations to honor those that have died. Día de los Muertos the Day of the Dead is the Mexican celebration of those that have gone before. What I find important is being comfortable with the past and being able to talk and celebrate with such an artful approach. Examples of expressing and honoring the dead are though making alters, paintings, costumes photography and films such as Coco.
Find the expression that suits you.