There’s a very common saying in Taijiquan:
“Keep your head so it feels like it’s hold up by a string.”
In fact, this is not just a tai chi statement. A lot of dancers, ice skaters end several other disciplines use exactly the same phrase
So, what does that mean? Does it mean that your head is on straight? Yes of course it does. Does it mean that you need to balance it all of the time, just like you were balancing a book on your head. No, it doesn’t. Certainly not.
What you need to realize is that the quote is not about balancing or forcing your head to keep the it up or straight. It’s very simple actually: Just stand in a wuji- or beginning [form] posture with your feet shoulder width apart. Stand straight and pay attantion to your jaws. Relax the jaws and all of the face face, relax the neck, the chest and let the breath sink to the lower abdomen. Relax all of your body, shoulders, knees, lower back. Make sure that you relax so much that all of those muscles you tend to use to hold up your body relax and does not interfere. If you stand balanced and relax your body this way, deeper muscles will take over, muscles that can take care of your structure all by themselves. If you let them to do so. It’s very funny actually, but if you relax deep enough, your body will keep up all of the structure by itself. You will feel that all of your body wants to rise, and you will feel taller, and more balanced than you did before you relaxed your body.
“Keep your head so it feels like it’s hold up by a string” means that your head rises and balances by itself. There’s nothing forced, nothing to control, nothing to worry about. Just let go so your body can teach you how to keep your head on straight.