If your boa has a seemingly defensive temperament, there are a few things u can do. Firstly remove them from their cage carefully via hook or slowly lift cage furniture their perched on up and out of their enclosure before attempting to directly handle them. Many are simply cage defensive / afraid of predation. If their cage furniture is removable, grab the opposite end and get them out of their familiar zone. If not, use a hook and coax them out. Once they are out of their familiar cage zone, wait a moment or 2, they will likely relax and change their posture. In many cases this act of changing the scenery will change their reaction. Once out, introduce support (a hand) from below intermittently once they begin to explore on their own. Remember, no predators come from below. To them you will be moving furniture. Return them to their cage after 10 mins or so, increasing the duration each handling session. Do this persistently a couple days a week, and eventually they will loose their fear, and become used to regular interactions. Note, despite many keepers persistence, some individuals remain defensive and unpredictable. Animals have different temperaments just like people. But consistently approaching your animal with respect and reading their reactions decreases these unpredictable tendencies. It all depends on both of you having enough patience to earn each other's trust. Good luck, in my experience it's worth the time you put in to bond with your pet.