Death is the complete and total disowning of yourself and all responsibility for who you are. It is an attempt to say "I am not eternal life", "I am not as God created me", "I am not even who I am".
The only way you can accomplish this disowning of yourself is on purpose, deliberately and intentionally. It is your own self that you have to give away and it is your power you must disown. You have to choose to do this.
This is why the Course teaches that "nobody dies but without his own consent". You literally have to choose to die. What this means is, you literally have to choose not to be what you really are.
But you can't actually stop yourself from being what you really are, because GOD is the one who has established what you are. You cannot go against his Will or change His mind. He created you for an eternity and you can never die.
So the idea that you can not be as God created you, or not be yourself, or be the opposite of Life, or have no Life in you, is merely an act of DENIAL. It is a denial of the truth that you are eternal life and can never die.
And so death is a choice to deny the truth, and is why "sickness is a defense against the truth." But denial of the truth is not the same thing as its removal. You can deny that God exists but this does not destroy God. You can deny you are not who you are or that your life is not your own or that you have no power or that you cannot be responsible for who God created you to be, but that will not change any facts. Denial isn't a fact. Death isn't a fact. It is a cover up.
Nobody has really ever died and nobody ever will. Death doesn't work and you cannot die. You may or may not transition into or out of bodies for whatever purpose, but what you are cannot die.
Since the illusion of death - the *denial* that you are eternal - can only seem to happen by choice, this also means that you can choose otherwise, and therefore you can choose not to experience death. If at some point you decide to 'lay the body down' or exit the physical form, it can be through true peace, power, truth and freedom, rather than some cause you didn't seem to want. And it will have no effect on you because you are eternal.
Truth is the way out of hell.