Anyone have any tips on taming an aggressive snake???

I have a pastel ball python that is about 250 grams. He was tame as can be when I bought him lasting for about a month. Now recently he has become overly aggressive. I can handle getting bit a time or two but he is unmanagable. The minute I open his tub he comes straight up at me in striking position then begins to strike when my hand comes close. Even after picking him up he strikes over and over and over. He also does the whole puffing, hissing deal. I don't know what to do, any suggestions are greatly appreciated.
Thank you!