Either you have control over your body and its functions when you sing or you don’t. If the control is fluid and the sound free, that’s all you need. Some people have that with almost no training, some work hard to get there, but either you get there or you don’t.
There are so many people who do not understand how to use their bodies well, and who are encouraged to pay attention to the sound and only the sound, or the music and only the music, or the acting by itself, or some other outside distraction. I am still surprised at the numbers of individuals who sing who can’t control very much of anything. The numbers have not decreased over the decades, even though we have learned more from voice science. I am reminded, though, that very few people read voice science peer reviewed journals and fewer still understand enough of what they are reading to make use of it. I think it would be fair to say that those who sing or teach singing who are highly motivated and interested in vocal function do not account for a large percentage of the profession over all. It’s no wonder, then, that things don’t really change very much.
In order to control your body you have to pay attention to what it does and how it does it. You have to notice what moves and how much. You have to notice how you feel during the movement and if you like it or resist it. You have to be able to feel and move the muscles in your body in a special way – differently than for normal every day life and differently from any activity other than singing. You have to be able to do very specific  things on purpose every time easily and fluidly, and then connect those same things up to the sounds you make as you make them. Every single time.
Being in touch with your body has levels and layers. You can perceive your body but if you do not actually focus your concentration deeply on what it is doing without distraction while it is doing it, the awareness you have could be at best vague or generalized, or at worst completely useless. You may not even know that you are not in touch with your body in this way if you have never encountered deep physiologic change. Perception here is not limited. You can perceive the five senses in myriad ways – but not if you are always being drawn to paying attention to external cues. There is no limit to conscious awareness, it continues to deepen and expand every moment of your life and the lamplight of your conscious choice is what illuminates that expanded state. In other words, what you pay attention to increases and why you pay attention gets clearer, more refined and more detailed. It’s not about “thinking” it’s about perception, and they are not the same.
If, when you sing, you are present in the sound, in your body, and in your emotions, and you are in control of all of them such that you can leave them alone and let them do what they do, you have achieved all that there is to achieve in your singing.
If you have not yet gotten there, don’t give up. If you have, strive to get back. If you are one of the blessed souls who can live there, share what you know with others who would find the same nirvana.