*WARNING! SPOILER ALERT!*
In my experience it starts about 18 months (earlier if you have more then one child), they start not wanting to give you things hiding it behind their backs. You will think this is cute after all they still have their baby chub and are cute (minus then toxic nappies). This is how they get you where they want you. This is their little plan all along! So it starts off pretty innocent, then it progress', they start walking more so cue the tantrums, they start talking more and the words 'NO' and 'MINE' seem to be the only ones they can ever speak, unless they want something then its all puppy dog eyes and 'yes please' (see their little plan).
Then it seems to calm down when they turn 3, normally you get about a few moments a week when your little angel can rival Lucifer himself. You think to yourself 'YES! We made it'
HA! HA! HA! Their little plan is still working 3 years on. Then they go to nursery(pre-school). Then they start with the independence where apparently they can walk themselves to nursery and they want to be like the 'big' kids they see walking to school. You try telling they even though they are a 'big' boy/girl they aren't that 'big'. In which they argue telling you all the reason why you are wrong.
Then finally they fall in to the swing of nursery and they settle again.
This is the calm before the storm. When I say storm I mean the worst storm created by a tiny human that you could imagine! They turn four and with it, it seems like they had a personality transplant or worse, some sort of possession.
You will find yourself wondering who the hell it is staring back at you through you beautiful angels eyes. The fact you remember them as your beautiful little angel means that their little plan worked. Just to cement this plan every so often you will see this little angel of yours.
Like I said it has been 2 weeks and I think I need to dye my hair as I am sure I can see grey from the stress. It is like he is completely different but the same all at once. His favourite word is 'NO' again. He demands everything and throws the biggest tantrum you could possible think of. However this tantrum is only because he asked a question and the first word wasn't 'yes'. He doesn't listen to the rest which if he did he probably would be on the floor AGAIN!
He obviously has more words now and just knows how to hit you where it hurts. I no this is a phase and hopefully it will pass soon. In the mean time deep breaths and counting to ten will have to do. Because drinking vodka and wearing ear defenders just is not acceptable!