The Lord by His life on earth taught us how to prepare for heaven. He showed us how to cooperate with Him to do the work of changing our character from one that is selfish, self centered, inconsiderate and fearful (living in a hellish way) to one that is kind, giving, generous and confident in the Lord (living in a heavenly way). This is a process and it takes time – a lifetime. As we make choices to turn away from selfish and merely worldly gratification and in turn make choices that are based on the truth, and inspired by generosity and kindness, we develop a desire or will for what is good. It is that will or dominant love within us that determines our place after the death of this body. If we primarily love what is kind, good, and true we will find our happiness in heaven where we can continue to live this way with others of a like mind and heart. If we primarily love what is selfish, hateful and deceitful we will actually find heaven an uncomfortable place, and instead find a place in hell where we can continue to live this way with others of like mind and heart. We therefore essentially judge ourselves - or choose our own eternity.
"I have come as a light into the world, that whoever believes in Me should not abide in darkness. And if anyone hears My words and does not believe, I do not judge him; for I did not come to judge the world but to save the world. He who rejects Me, and does not receive My words, has that which judges him—the word that I have spoken will judge him in the last day." (John 12:46-48)