Alfred, I don't think this is a classic fear of death that some people get that has to do with fear of injury, or fear of disease.
I think you're going through a midlife crisis kind of early and you have a fear of being insignificant, and you've reached the stage of thinking "Is this IT??? Is this all I'm going to get out of life?"
I think what would help you right now is to take up doing something that's very significant that will leave a legacy on the world.
Follow a passion that will make you significant to someone - start an adult literacy program, a bikes for kids program, take your family on an absolutely unforgettable adventure, etc. Something that will give you new energy and make have impact on people around you.
Best wishes. I do wonder why you posted in the child behavior forum - your question may get moved somewhere else.
Have to agree with heartfluttersflyawayplz. If you do not yet know Jesus as your savior, that would be a great first step. If you don't have Him as your savior, there is reason for concern. If you have Him as your savior, you can rest assured that when you die, you will be with your creator in a much better place. While you are living, He will give you all you need, including comforting and encouraging you when you need it. Cry out to Him and let Him be there to help you.
so sorry your going throught this. Death is a very scarey thing and i belive most think about it sometime or another. anxiety can cause thoses feelings and make them worse. your wife needs to be more understanding and listen to your concerns that would help you . if shes does not than find someone who can be there for you and you can lean on. yes life goes by fast so live it everyday not scared if you can. GOD will give you peace when you need it, pray to him. and know when this body is gone what a much better place we will live if we took him s our savor. GOD bless you .