There is a training scale in classical horse training through which all well-prepared horses are taken to unlock their full potential. The scale is often depicted in the form of a pyramid, beginning at the base with rhythm and culminating at the top with collection. In between are suppleness, contact, impulsion, and straightness, in that order.
In horse training, rhythm is the result of mental and physical relaxation. Rhythm is compromised when there is tension, so the first point of order when training a horse is to work in a way that discourages tension and encourages relaxation. Few things relax a horse more than a rider who is deeply relaxed himself.
When a horse is sufficiently relaxed he will walk in the natural rhythm of the four natural gaits: walk (4 beats), trot (2 beats), canter (3 beats) and rein-back (2 beats). The goal when working to establish rhythm is to not only establish a definite 4, 3 or 2 beat gait but to also maintain a steady tempo.
On a similar note, my eldest son and I are studying violin and cello, respectively. We’re learning the importance of rhythm in music and just like with the horses, rhythm comes much more easily when the musician is relaxed. A metronome may help train the perception of rhythm but at a certain point you must relax into the rhythm. You know you’re sufficiently relaxed when you can anticipate the rhythm.
Rhythm, in this sense, is both a matter of the mind and the heart. You can “get” the rhythm to a certain degree, but in another sense you have to let the rhythm get you. Gloria Estefan was right!