3.33

सदृशं चेष्टते स्वस्याः प्रकृतेर्ज्ञानवानपि ।
प्रकृतिं यान्ति भूतानि निग्रहः किं करिष्यति ॥

sadṛśaṃ ceṣṭate svasyāḥ prakṛter jñānavān api
prakṛtiṃ yānti bhūtāni nigrahaḥ kiṃ kariṣyati

śrībhagavān (श्रीभगवान्) is speaking, and even the knower is put back under nature for a moment.

The verse

Even a man of knowledge acts according to his own nature; beings follow nature; what will restraint do?

नेपालीमा

ज्ञानी मानिस पनि आफ्नै स्वभावअनुसार चल्छ। प्राणीहरू प्रकृति पछ्याउँछन्, निग्रहले के गर्ला।

Where it sits

3.29 told the knower not to unsettle the dull, and this verse says why the unsettling would fail: beings act from nature. 3.34 names the two forces inside that nature which he must not come under, and 3.35 sets his own dharma above a borrowed one.

Split: सदृशम् + चेष्टते + स्वस्याः + प्रकृतेः + ज्ञानवान् + अपि + प्रकृतिम् + यान्ति + भूतानि + निग्रहः + किम् + करिष्यति

sadṛśam + ceṣṭate + svasyāḥ + prakṛteḥ + jñānavān + api + prakṛtim + yānti + bhūtāni + nigrahaḥ + kim + kariṣyati

Sanskrit, in depth

The words

देवनागरीWordGrammarSense
सदृशम्sadṛśamaccusative, adverbialin accordance, in the likeness.
चेष्टतेceṣṭatepresent, 3rd singular, middlehe acts, he strives.
स्वस्याःsvasyāḥgenitive feminineof his own.
प्रकृतेःprakṛteḥgenitiveof nature.
ज्ञानवान्jñānavānnominativeone who has knowledge.
अपिapiindeclinableeven.
प्रकृतिम्prakṛtimaccusativenature.
यान्तिyāntipresent, 3rd pluralthey go, they follow.
भूतानिbhūtāninominative pluralbeings.
निग्रहःnigrahaḥnominativerestraint, holding back.
किम्kimnominative or accusativewhat.
करिष्यतिkariṣyatifuture, 3rd singularit will do.

The phrases

सदृशम् चेष्टते स्वस्याः प्रकृतेः ज्ञानवान् अपि sadṛśaṃ ceṣṭate svasyāḥ prakṛteḥ jñānavān api is the limit on knowledge as a brake. Even the man of knowledge acts in the likeness of his own nature. प्रकृतेः + ज्ञानवान् prakṛteḥ + jñānavān is prakṛter jñānavān (प्रकृतेर्ज्ञानवान्). ज्ञानवान् + अपि jñānavān + api is jñānavān api (ज्ञानवानपि).

प्रकृतिम् यान्ति भूतानि prakṛtiṃ yānti bhūtāni widens it from the knower to beings. Beings follow nature.

निग्रहः किम् करिष्यति nigrahaḥ kiṃ kariṣyati is the question the two statements force. What will restraint do? The subject is nigrahaḥ (निग्रहः). Holding-back is not going to cancel the nature they move by.

Sanskrit in this line

jñānavān (ज्ञानवान्) is the nominative of a stem in --vant (वन्त्), "possessing knowledge." The nominative lengthens the vowel and adds n (न्): jñānavān (ज्ञानवान्). You met this shape on vīryavān (वीर्यवान्) in 1.5. api (अपि) sits on that nominative: even he. The knowledge is real, and the verse still sends him with his nature.

Say it back

Who still acts like his nature, and the question about restraint. If the answer you supply is a method of restraint, you have not stayed with the verse. The verse asks what restraint will do, and does not give it a victory.