GW, I understand perfectly. When she hit that 3 year mark, man oh man, did I get a rude awakening. This age is all about independence & they want to do everything on their own & they want to help with everything. They start with the copycatting & repeat everything you say, which annoys the living daylight out of me & believe me, that still goes on well after 4

Luckily my daughter is turning 5 in Oct so it has gotten alot better.
Yes, there will always be challenges with each age as it's never going to be a breeze. We do occasionally bump heads because of other things but nothing too major. Overall she listens to me & does what I say.
The only problem that comes into affect when they turn about 4 is; fears fears fears

PRESCHOOLERS (3-6 years) imaginary figures (e.g., ghosts, monsters, supernatural beings, the dark, noises, sleeping alone, thunder, floods)
My lg fears all of the above except floods hahahaha.
Since Jan this year I've been struggling with her to go to bed on her own. She always went to our bed 1st & then I just put her ladybird on that makes stars on the ceiling & she would be okay if I left her. She also knew that she will be taken to her bed later on

but now I have to lie next to her until she sleeps. She is just terrified of the dark, ghosts, monsters etc. It does get exhausting with times. She was very bad in the beginning because she would be like that in daylight as well. I would have to go with her when she wants to use the toilet, fetch something in her room etc but we do have some good days with it. I know this is normal behaviour for her age but it's hard cause I don't now how to ease her mind. You can't just tell such a small child she is just imagining things & so on cause to them it all feels so real & they don't understand everything.
I'm very cautious with what she sees on tv but you can't control everything they watch at school or hear from other kids.
Sorry for the long post............got a bit carried away!!!