Mind in dantien is a natural physical response to stress. Consider the most stressful situation imaginable: your walk to the gallows. The gripping in your belly would be so intense that in all likelihood you'd both vomit and shit yourself: indications that your body is centering itself and preparing the spirit for an unavoidable confrontation with death. The same happens when soldiers are readying themselves for battle, or when stage performers are awaiting their grand entrance. The prospect of spirited transformation is awful because spirit is your own internal other and, when it shows itself, you have no idea (thought) of what you'll become or of how (well) you'll perform; it is the absolute unknown. Nowadays, however, we have made for ourselves a completely artifical environment where spirit never needs to show itself with any life-saving or life-threatening intensity. So the modern response to stress is not a wise and spirited withdrawal of mind into dantien (where it can't get in the way and mess things up) but worry.