After a time you really get to know your snakes body language. Everything from how tense their muscles are to the speed they move to even the way the tongue flicks tells if they are nervous, hunting, or calm. I can usually tell when Maru is stressed out and when he's not. Honestly he is the most stressed when I am. If you aren't comfortable, don't let him do it. Getting nervous and panicking causes more bites around here than anything else. We move different when we are nervous, snakes are sensitive to that. It's frightening to be held by something that is unpredictable! I've personally decided a bite is a bite, I've been bitten by dogs, cats, and parrots before and all of those are more painful than a snake bite so I just roll with it. I'm confident and I just keep my cool when holding maru. I've let him go up to me before when I could see he was just curious and everything was fine. It's been three years and I have not been bitten yet! We'll see how long that lasts(lost my snake tongs..Been having to feed by hand. Boy I'm just asking for trouble aren't I! :D)