It's not you. It's the machines.
If it seems like it's impossible to win a stuffed animal from a claw machine, well, it kind of is. This video from Vox explains that claw machine users "are not the problem. The claw machine is the problem." Claw machines are programmed to make sure they earn their owners money. The claw doesn't always use full strength and it also has the ability to drop what it picks up.
Now if only science could explain why we're compelled to try, and try, and try again.