Confidence, man. If you are afraid of your snake it is training you to not pick him up.
So, either accept that you are going to get bit, which can be difficult for many. Even if they have velco teeth. Or use a glove or snake hook to retrieve the animal and do not reward any aggression with a quick return to an enclosure.
These snakes are not athletes, they will tire pretty quickly.
Since your snake was great handling wise before you can remain optomistic that he will be again as it isn't one of the occassional ":cens0r::cens0r::cens0r::cens0r::cens0r::cens0r::cens0r:" snakes we sometimes come across. Luckily some people enjoy the feistier critters for there attitude all the more anyway.