Yogis who strive see this Self established within themselves. But those who strive without having refined their inner selves, and who lack understanding, do not see it.
Explanation
Krishna continues from the previous verse, where he said that only those with the eye of knowledge (jñāna-cakṣus) perceive the Self as it leaves, stays or experiences the world. Here he adds that effort alone is not enough: yogis (those disciplined in spiritual practice) who strive do see it, but those whose inner self is unrefined (akṛtātman) and who lack discernment (acetas) do not, however hard they try. Commentators differ on what this refinement chiefly involves, such as ethical discipline, devotion or knowledge, but agree that it is needed.