Fear of death is mainly caused by misunderstanding death and its consequences or because of fearing the bad results of sinful acts.
Death is a definite stage in the life of every human being and it does not mean a disaster but a transfer from a stage of life to another stage in which good people will enjoy the great reward and Mercy of Allah, while bad people will meet the results of their own deeds.
Believing in The Mercy of Allah should make us hope to get from His Mercy whether we are alive in this world or after this world.
Death is the start of the happy life of the believer as well as the start of punishment of the enemies of Allah.
Always trust and hope to get from Allah's Mercy and repeat: YA ARHAMARRAHIMEEN. Repeating Salawaat and Estighfaar is also very useful in getting peace of mind.