What you're perceiving as "aggressive" is actually just fear. They are "nervous", and that's why they are nippy. They don't bite out of meanness or spite, just out of fear. In their world there are two kinds of creatures. Those that are small enough to be eaten and those that are large enough to eat them. You fall in the second catagory, so naturally they are afraid. Only through regular, gentle handling will your JCP learn to trust you. I have two JCP's, one bit me everytime I picked her up for about a year, the other is totally docile. When the biter has bitten it wasn't bad, just a quick nip and let go. When she did that, I'd never drop her or put her right back in her cage. I think she learned that biting wouldn't get me to put her down, and eventually learned that I wasn't going to hurt her and now bites infrequently. Good luck and keep us updated with your progress.
Kirk

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1.1 Jungle Carpet Python
1.1 Ball Python
1.1 Corn Snake
0.1 Gray band Kingsnake
0.1 Desert Kingsnake
0.1 Pueblan Milksnake
1.0 Bullsnake
1.0 Rhodesian Ridgeback (Hondo)
0.1 Spouse (WC)
0.0.8 hatchling ball pythons