Here's a few sections copied and pasted from my reply to someone else asking the same question a few months ago.
You are a huge, unknown creature; he is a prey animal. If he thinks you are going to grab him every time you walk up to his box, of course he's going to struggle. If a predator grabs you, you go into fight or flight mode. If you can't flee, you better damn well fight your ass off if you want to live.
That said, let him relax in his new digs. Change his water, monitor the temps, that's it. Allow him to become comfortable in his own area, let him feed in peace, and once he will bask in your presence without startling, you can start slowly introducing yourself in a non-threatening manner.
First just stand by the cage. Then, after a few days of that, open up the door for a few minutes, close it, walk away. Then, eventually, place your hand inside NOT neat the lizard. Then place your hand inside and offer food (as in dump a few crickets or what have you). Then place your hand inside and offer food from tongs. Don't be pushy, move at the lizard's pace. If he runs, try again in a couple days. It can take weeks.
My Savannah will come up to me if I open the door (not because I'm interesting or her buddy, she just knows that ME OPEN DOOR often = FOOD. The trick is to make your presence reinforcing. Get over any notions that your lizard will be your friend. They will tolerate your presence, they will tolerate being handled, but if they could, they'd probably avoid you at all costs.
Your monitor needs time. The more you rush the "taming process" the longer it will take. He needs to learn that your presence isn't something to fear. This will happen more quickly if you do things gradually. It's called desensitizing. Imagine if someone was deathly afraid of spiders. Then imagine putting a large tarantula on their shirt. Do you expect them to stop freaking out since the spider isn't hurting them? No. They won't stop freaking out because they are too caught up in their fear to learn anything.
This is most likely what happens every time you pick the lizard up. With this method, one of two things will happen. First, the lizard will fight and bite and tail whip until you put him down. Thus, lizard learns that fighting will fend you off. On the other hand, if you continue to hold him and tolerate the fighting, the lizard will shut down mentally and live in a state of learned helplessness. No use fighting since I can't win. I can't flee so I better just accept that I am helpless. This method does not allow for a thinking creature you can interact with.
Now, back to the hypothetical situation, imagine that same person with arachnophobia. Put them in a room with a picture of a small, beautiful spider. Let them get used to that at their own pace. After a few days of that, show them a movie of the spider moving. After a few days of that, show them a spider in a container across the room and allow their natural curiosity to draw them to it. And so on and so forth.
Which method is better? The first method might obtain results faster, in that your lizard no longer thrashes and fights when you handle him. However, he'll constantly live in fear. Instead, slowly increasing the "criteria" only when the person is comfortable with the last set, and making each experience reinforcing is the key.