Both my Burms started as quite feisty little fellas. They would hiss a lot when I tried picking them up and sometimes even when cruising my hands. Got bitten a few times, no big deal.

The older one, now that he's around 5ft, became super mellow. He'll still hiss a bit if I disturb him while sleeping but otherwise he's puppy dog tame. My favorite snake now. I just open the cage and he comes out on my hand on his own.

The female is still young and scared, still working on her. She's already better than when I got her, no biting anymore and stops hissing soon after I pick her up.

Just work with your animal and you'll see results, I have the impression they're a bit smarter than other smaller snake.