Ours got wilfull and determined at just around that point. Also, he doesn't talk. We make sure he gets out a lot, a well worn child tends to be more placid/ malleable in the house. The other thing we've got going is, I now know what the I need help whimper sounds like, sometimes I give him a few chances to work it out for himself, sometimes I offer him a helping hand.
If in the case of the cabinet door, he is doing something which he really ought not be doing, we might say - No, no opening the cabinet, that is not a toy. then follow with a gutteral, "eh!!" kind of like you might hear Ceasar Milan doing with his dogs. If he doesn't relent, we pick him up bodily, kicking and screaming, and move to a totally different part of the apt and get involved in something totally different.
If it is something which is dangerous, the intervention is swift and immediate. No, you may not go into the kitchen when there is broken glass on the floor. Remove DS from the kitchen, hold him kicking and screaming if necessary. Have a conversation about the broken glass, that its sharp and that he will hurt himself, and that mommy & daddy love him and don't want to see him hurt once the kicking and screaming have stopped.
He is 20 months now, and has a solid understanding of "no." He qets quite upset actually when grandpa says it. He doesn't always comply, but I am confident that he gets it.
Keep at it, I hear it gets better when they hit 18 years old. Meanwhile, if you can get yourself a few nights/ days rest, you will be better able to deal with your little one.
Good luck to you and yours,
F. B.