Usually it is stressful, especially when the handler is inexperienced.
But like I said before, they get accustomed to not minding handling. They may enjoy your warmth, or your security sure, but can we really know? Probably not.
When your JCP climbs on your arm, it may be because he knows that when he gets to go out, he gets to slither around more and exercise and has associated this with handling, which naturally and instinctively is probably enjoyable.
Just my thoughts. :]