The Other Side

This is about the other side of parenting. The side that makes me want to pull my hair out. The side that leads me to dislike myself. To ask, how can someone I love and adore so deeply leave me so frustrated? So unsure? So certain I'm doing it wrong but without any idea how to get it right.
Our son is 3. Almost 40 months, to be more precise. At this point, he rarely listens to me without multiple requests, threats, and/or promises.
I don't want to use threats or promises (i.e. bribes). I want him to be motivated, to be disciplined, to be cooperative. I don't want him to be browbeaten. I don't even want him, in the long run, to be subordinate, which may be part of my problem. He has mastered insubordinate.
Basically, I want him to do what I want him to do, without being forced to do so. That is so not happening, except for the rare occasions when what I want happens to coincide with what he wants.
I try to motivate him to want what I want, but really, at three, is he likely to want to brush his teeth? I don't even want to brush my teeth. I do, usually, because I understand the consequences of not brushing my teeth. So I inform him of the consequences of not brushing his teeth, I try to make it fun and enjoyable, I give him as much latitude as possible to do it himself without being completely ineffective, and I praise him whenever reasonably possible.
And yet we struggle over tooth-brushing and countless other opportunities for resistance.
I threaten time-outs, and I impose them when the threat (or warning, I suppose) doesn't produce the desired result.
I don't want my three-year-old to walk all over me, but I don't want to crush his spirit either. I seem to be skidding back and forth across this parenting highway.
I know that there are methods and rules that I could be following, but I'm reluctant to make J behave for all the wrong reasons. I'm afraid that he'll end up like his mom -- aiming to please, afraid to say no, lacking confidence, and seeking reassurance.
I remind myself that parenting didn't seem like such a struggle just a few short weeks ago. And the past few weeks I have been heavily occupied with other things. We also spent three nights last week bunking at my in-laws' place, which probably didn't do much for my parenting authority, among other things. In that light, he's probably craving good times with me as much as I am craving good times with him.
We can get back on track.