Often you'll find that snakes which are fine to handle once they are in the hand are, nevertheless, very defensive when you first reach into their homes to pick them up. This is because your hand is only understandable to them as a predator.
The trick is to be quick and sure in your actions. Jungles virtually always get much tamer as they grow, especially with constant handling, so don't worry.
Remember that the more relaxed and sure your movements are, the less like an enemy you will seem to the snake. A few nips from a youngster are well worth it when you end up with a calm and handlable adult.
Good luck
G