What Jesus meant was that whoever is attached to the worldly life and this earthly body will lose them in death. But whoever lets go of attachments to this worldly life and this earthly body and identifies with the permanence or God-consciousness that Jesus represented, will never die.
Rama SwamiIt was Lord Jesus Christ who said "Whosoever will save his life shall lose it, but whosoever shall lose his life for my sake shall save it. For what shall it profit a man, if he shall gain the whole world, and lose his own soul?"
Rama Swami