A dancer's body and a dancer's partnership (the two-headed four-legged animal) have natural physical limitations. The advanced (trained) Ballroom Dancer uses these physical limitations when moving as an individual or moving as a partnership.
I like to use the analogy of a bicycle's handle bars. If you sit on a bicycle and turn the handle bars as far as you can in either direction, they will hit a physical stop on each side. This is the physical limitation of the bicycle's handle bars. The turning of the bicycle is limited by these physical stops for safety reasons. The dancer's body and partnership have similar physical limitations. I call the bicycle's (steel) handle bar stops, "hard stops". I call the dancer's (muscle) stops, "soft stops".
A general rule in Ballroom Dancing is "once in motion, it continues in motion until there is a natural (soft) stop". The "it" may be anything. It could be a body, an arm, a leg, the head, the partnership, etc. The key is to allow the movement until there is a natural conclusion. This takes some practice to be able to allow the motion of the movement to continue. The inclination is to stop the movement early, before the "soft stop". Once the dancer acquires this skill, the movement becomes much easier and natural. This skill also causes the movement to be smoother and more exaggerated. Basically, the dancer allows the movement to continue until a "soft stop" is achieved.
Here is an example of a dancer's natural "soft stops". Turn your head to the right until you feel your neck muscles restricting your movement, then turn to the left in the same manner. These are your necks "soft stops", just< the same as the bicycle handle bars had its "hard stops". The partnership has "soft stops" as well. An example would be when one of the partner's movements is impacted by the other partner.
The following are dance pattern elements that should contain "soft stops":
The "thigh slapper" element in American Style Tango. The lady's Ronde continues until her thigh contacts (slaps) the man's thigh. Generally speaking when a leg is executing a Ronde, the leg continues to rotate until it contacts the other leg as the "soft stop". In a "drop Ronde" element the leg is extended because of the bent supporting leg. This results in the thigh becoming the "soft stop". In a Waltz "whisk" element the leg is almost straight because the supporting leg is on "rise". This results in the "soft stop" being a wrapping action around the supporting leg.
The "frame action" and "hip action" elements in a Tango "promenade close" element. The sudden stop causes the lady to swivel from promenade to closed dance position. The "soft stop" of the leader's frame allows the lady's frame to transition from promenade to closed dance position. When the frame stops, the lady's hips continue to rotate until they find the dancer's "soft stop". In this example, there is a partnership "soft stop" and an individual dancer's "soft stop".
The "head rotation" element in all Smooth/Standard dances. In a link to promenade action, the dancer usually stops the rotation of the head based on line of sight. Allow the head to rotate until the "soft stop" is encountered. This gives the link a more exaggerated look and results in better partnership balance. In a Tango triple head flick, the exaggeration gives this element an impressive flair.
The free arm in the Rumba "crossover break". The free arm in the crossover break doesn't just extent to the side, it moves backwards until it hits the "soft stop".
The Bolero "sit break" element. The action of the break continues until the "soft stop" of the hand connection is encountered and a skid forward results.
"Latin/Cuban Motion". The action of the hips settling is an example of allowing the action to continue until the "soft stop" is encountered.
There are many examples of individual dancer's "soft stops" and partnership "soft stops" in both Smooth/Standard and Rhythm/Latin styles of Ballroom Dancing. It seems to be human nature (men and women) to short cut movement actions in Ballroom instead of letting them continue to a natural conclusion. Allow the movement of the partnership and yourself as a dancer within that partnership to be free and encounter all of the natural "soft stops" along the way.
Allowing all of the "soft stops" along the way will give your dancing a new look and feel. Your dancing will have that smoothness and control that we all are trying to achieve. Just continue the movement until you hit the "soft stop" (Bicycle handle bar stop).