Fear is a normal human response to any threat ( seem or unseen). If fear is within limits it usually increases our performance e.g, Fear of examination makes us read more. But excessive fear leads to anxiety and decreases performance.
Next Steps
As death is an inevitable thing. You should prepare for It rather than fearing it. By preparation I mean, to do righteous things and avoid doing sins ( within your religious faith). Doing this will hopefully overcome your fear of death as good reading by a student helps him overcome the fear of examination at the end of year.