The human body gets sick, rots and dies.. is basically a machine.. Personal Identity with the human body is a mistake.. Its a disquise even a "space suit".. for the spirit.. Jesus (to my reading) tryed to wean the disciples of identity with the human body.. to identity with the spirit.. Capsulated in the "born again" metaphor..
Personal Identity with the human body, "your" human body, can blind you to what Jesus was saying, teaching, even showing.. As Jesus said, "the flesh means NOTHING, it is the spirit that counts".. Jesus treated his human body as clothing he identified with the Spirit.. Jesus's human body was not who he was but only who he appeared to be.. He was far MORE than that.. And as he said... SO ARE WE.. i.e. I Cor 2;9..
Dear hosepipe, Christianity early on dealt with that sort of platonic dualism with the early Gnostics. The first thing I would point to is that when God created the universe, including man, he declared it was very good. There is nothing inherently bad about the human body. That is part of who we are. When sin entered it effected the body but it also affected the spirit. Sinfulness affects the spirit just as it effects the body and even for those who come to a knowledge of what redeems both body and spirit they are still left with the affects of sinfulness to the spirit short of glory. We know that once we attain glory we shall be reunited with our bodies and our body and spirit shall be perfected just as it was with the original man and even moreso.
One of the major errors of the Gnostics was their claim that Jesus did not really come in the flesh and this is a natural consequence of Platonic dualisms. If the flesh is all bad and Jesus is all good then it would be inconsistent to claim that Jesus came in the flesh. But Jesus did come in the flesh to redeem the whole man not just his spirit otherwise he would not have been incarnated. I'm afraid your reading of Jesus in his depiction of the flesh and spirit is too literal and does not take into account that his reference to flesh does not refer to the organic substance per se but the results that sinfulness has upon man's thinking and feeling and willing such that his actions are directed towards himself as a whole being first and not directed towards God who is spirit and the source of man and from whom we receive all wisdom. If we take this view then we can rejoice in our bodies and souls as one being created by God as very good in its original constitution and being redeemed as a whole being we can put our being in service to God as that for which we were originally designed.