Remember, as humans we all have a fear of death - crossing the threshold is only performed once, with the latter thought the experience is a new feeling; Hebrews 9:27.
Sure, as believers we look forward to being with God, but the human characteristic of death is strangely odd; an unfamiliar condition.
All physical beings (even animals) cling to life (the struggle) - in this world it is all we can clearly understand.
When you become older adjusting to the fact will become obvious and more peaceful.
Furthermore, what you are feeling is completely normal, at a certain age in life (17-22) the thought is most concerning, perhaps even frightening - we look for older people to speak about the subject but then realize they are in the same situation.
Finally, make your peace with God, attend Church and recite your prayers each night will provide comfort.