I have 2 of the terrible 2's so I know what your going through. I think the more you work with them the better they are. They still have that "I'm going to test you today" attitudes so you can't let your guard down like you can with an older horse. One time you think you have a bad habit gotten rid of and the next day its back.
They have really short memories at that age so consistency, patience and eyes in the back of your head
are your best weapons.