I don't think all deaths are, what about those whom die instantly in accidents etc? You don't know its happening, so no time to be scared or feel pain? Or if there is pain, you won't have time to register it before lights out.
Death you are aware of, could be scarey, esp if you are not ready, but I have read many a story of people esp the older one's, who have made peace with dying and go calmy with no fear and no pain
If you speak of suicide though, as a separate death, then no matter how prepared you are, I do think there is a element of fear regardless, as for pain? Who knows?