The best way to calm agressive animals is usually to handle them, and with snakes, avoid feeding them in their enclosures. This can form a feeding response where they'll strike as soon as you open up their cage.

If you use a separate feeding tub, just the handling that happens while movin the snake from cage to tub, and tub to cage when he's finished eating can be enough to calm him down over time.

He'll get used to the fact that when you put your hand in the cage, food isn't coming immediately, and he'll also get used to the fact that when you pick him up, something good is going to happen.

It may take a while depending on his age, and how long he's had the attitude, but stick with it.