धृत्या यया धारयते मनःप्राणेन्द्रियक्रियाः।योगेनाव्यभिचारिण्या धृतिः सा पार्थ सात्त्विकी॥
dhṛtyā yayā dhārayate manaḥ-prāṇendriya-kriyāḥyogenāvyabhicāriṇyā dhṛtiḥ sā pārtha sāttvikī
Word by word
The verse says
The steadiness by which a person holds the workings of mind, breath and senses together, through practice that does not waver: that steadiness, Arjuna, is clear.
In plain words
Now steadiness, and the first kind holds three things together.
Mind, breath, senses. Not one of them. The three at once, which is what makes it difficult.
And it is done avyabhicāriṇī - without wandering off. Not by force. By a practice that simply does not get abandoned.
Where you've felt this · in health
Your father has walked the same route before breakfast for about twenty years. On cold mornings he walks it. When he had a bad week at work he walked it. It is not an impressive distance and he has never described it as discipline. He has just never had a conversation with himself about whether to go.
Going deeper
Steadiness that never enters negotiation is what this describes, and it is cheaper than the kind that wins arguments with itself every morning.
The word means not wandering. What does not wander is not the body but the intention. A practice becomes steady at the point where it stops being re-decided daily, and until then every single session has to be paid for with willpower.
That is why it holds mind, breath and senses together rather than just one. A practice that is still being argued about occupies the mind, which is precisely the faculty it is supposed to be settling.
The practical consequence is counterintuitive. Making a practice smaller often makes it steadier, because a small thing survives a bad week without a debate, and a thing that survives bad weeks is the only kind that accumulates.