People have been trying to answer since we`first came on the scene whether one believes in creationism or evolution.
The scientific definition of death is that all life functions cease to exist. We lose all ability to feel pain, etc. If one has been suffering from a debilitating, painful, or terminal illness, death can be a wonderful release for the family as well as for the one suffering. There is some scientific evidence that immediately upon death, the body weighs less than when the person was alive, thus giving some credence to the existence of spirit.
Let's examine this topic from a theological standpoint. Most major faiths believe that the soul, or spirit, leaves the body upon death and has some form of continued existence. Before the time of Christ and for a while after that, one particular sect of the Jewish faith, the Sadducees believed that there was no life after death; that group ceased to be. The Pharisees believed in spiritual life after death.
Some pagan groups, or animists, believe that upon a person's death the spirit will inhabit a rock, a tree, perhaps an animal, etc. How long they believe that spirit stays there I do not know. Some Eastern faiths believe in reincarnation unless the soul of the person who died had existed on this earth either for a certain number of cycles, or until he/she finally "got it right" and could be reunited with the overarching life force, in other words, having reached Nirvana. Remember, these groups also believe in multiple gods.
So, of the three monotheistic world religions, all believe in the existence of spritual life after physical death. All three, Christianity, Judaism, and Islam believe in a judgment day of various sorts. The Koran pretty much states that (with perhaps a few exceptions) Muslims do not sin and get an automatic pass into heaven, which differs for male spirits and female spirits. The Koran says that all nonbelievers are infidels and will burn in Hades.
I find no comfort in that belief, first of all because I am a woman and would be considered much inferior to a man, and secondly because I will never convert to the Islamic faith, so if they are correct, I WILL burn in he*.
I find the most comfort in believing Christ suffered and died to cover my sins. We have several eyewitness accounts that he performed many miracles, including raising Lazarus and others from the dead. We also have many witnesses (their accounts found in the Bible), that saw Jesus in His resurrected form and spent 40 days with him after his resurrection. Of all the faiths I have looked into, I find this to be the most comforting and believe that since I confess Jesus as my Savior, His blood atoned for my sins; thus, He will claim me as his own and I will go to heaven.
St. Paul said that he was caught up (in the spirit) into the third heaven. He also said if we knew how superior it is to our earth we would all commit suicide to hurry there. He said he was forbidden from speaking of its wonders and beauties for this very reason.
I, for one, do not trouble myself with imagination as to what it will be like. It is enough to know that there will be no tears, no pain, only bliss and joy. We also know it will be a busy place and not a place of boredom. Remember, God reconciles all things, so if something is important to you here (such as a beloved pet), it will either be restored to you in heaven or you will have no recollection of it so it would cease to have important to you. Either way, this comforts me.
Death is inevitable. It is our choice how we face our own mortality. Many people do not fear the idea of death itself but rather fear the process. I am not so macho as to have no fear of the process. Will my death be painless? I don't really want to know what kind of dying experience I will have.
It is my hope and prayer that whatever your belief system, you may find peace before your time is up. And, for the record, I believe in heaven and hell. Without evil and Satan, Jesus' sacrifice would have been in vain.