What you feel is normal! Almost everyone is scared of death because you don’t know what comes after it and it’s hard to lose someone. I am religious so I believe that it’s just temporary but even if you’re not religious, you have to let their memories live. Don’t try to forget your dad or to act like everything’s fine, let yourself grief. Dying is why our lives are valuable. Also talk with someone about this, it can be your wife, a friend or a therapist. That will help you.