Well, ready to sounds similar to passive suicidal ideation. Example: you question if you would be motivated to jump out of the way of an oncoming car or accept it.

By mentally prepared I mean that you have an understanding of your own mortality and accept that life will end at some point without having mental or emotional stress at the thought(s).

Edit: Passive Suicidal Ideation is a sign that assistance may be needed. Anyone struggling with this please reach out to a therapist, memorize your prevention hotline, or throw out other lifelines. I had my struggle, but I will continue because I must. I can't rely on others to remember those important to me, or mourn them as they deserve.