Sthitaprajñya in the Bhagvad Gita 2:54-2:58, 60

I request you to read Vinoba Bhave's "Talks on the Bhagvad Gita" in which he covers both karma yoga and the concept of Sthitaprajñya beautifully. You can find the complete book online here: http://www.mkgandhi.org/talksongita/talk_gita.htm 

How does one describe him who is of Steady Wisdom ... Who is steadfast in deep meditation Krishna? How does he who is steady in Wisdom speak? How does he sit? How does he move Let us begin with Arjuna's question, trans. first:

2:54
स्थितप्रज्ञस्य का भाषा समाधिस्थस्य केशव 

स्तिथधीः किं प्रभाषेत किमासीत व्रजेत किम् 

स्थितधीः He who is steady in thought; both  आसीत & व्रजेत are in the optative - 'how should he'? 

Anvaya:
केशव, समाधिस्थस्य स्थितप्रज्ञस्य का भाषा
स्थितधीः किम् प्रभाषेत किम् आसीत किम् व्रजेत

Now we'll go to Shri Krishna's (2:60) warning before the description:

(The) turbulent senses carry away the mind forcibly, Arjuna, even of the striving man of Wisdom.

यततो ह्यपि कौन्तेय पुरुषस्य विपश्चितः 

इन्द्रियाणि प्रमाथीनि हरन्ति प्रसभं मनः 

Vigraha:

यततः हि अपि कौन्तेय पुरुषस्य विपश्चितः

इन्द्रियाणि प्रमाथीनि हरन्ति प्रसभम् मनः 

Anvaya:

कौन्तेय हि प्रमाथीनि इन्द्रियाणि अपि यततः विपश्चितः पुरुषस्य मनः  प्रसभम् हरन्ति

Arjuna, indeed agitated/churned up senses carry away forcibly the mind (even) of the striving man. 

यततः is an active present participle, and gives the sense of  present continuous '-ing' -happening, doing, striving. In Sanskrit this is called the वर्तमाने कृदन्त 
प्रमाथीनि is from√मथ् churned, whirled
विपश्चितः is from√विप् inwardly inspired, whose चित्त is inwardly inspired

2:55 The Blesses Lord spoke: When he abandons all desires emerging from the mind, Arjuna; And is contented in the self, by the Self, then he is said to be one whose Wisdom is steady.

प्रजहाति यदा कामान्सर्वान्पार्थ मनोगतान् 

आत्मन्येवात्मना तुष्टः स्थितप्रज्ञस्तदोच्यते 

Vigraha:
प्रजहाति यदा कामान् सर्वान् पार्थ मनोगतान्
आत्मनि एव आत्मना तुष्टः स्थितप्रज्ञः तदा उच्यते 

Anvaya:
पार्थ यदा मनोगतान् सर्वान् कामान् प्रजहाति 
आत्मना आत्मनि एव तुष्टः तदा स्थितप्रज्ञः उच्यते 

We have to supply the 'asti' after तुष्टः the sentence comes together. but as you know, the asti is often assumed and dropped in verses.

When (a man) abandons of all the desires that arise from (his/the) heart; is happy/satisfied by his-self in his-self, then he is known as a sthita-prajña. 

√प्र+हा - relinquish,leave behind, abandon

2:56 He whose mind is not agitated in misfortune, whose desire for pleasures has disappeared, whose passion, fear and anger have departed, And whose meditation is steady, is said to be a sage.

दुःखेष्वनुद्विग्नमनाः सुःखेषु विगतस्पृहः 

वीतरागभयक्रोधः स्थितधीर्मुनिरुच्य ते    

Anvaya and vigraha is pretty much the same for this verse.

दुःखेषु+अनुद्विग्न+मनाः सुःखेषु विगतस्पृहः  

वीत+राग+भय+क्रोधः  स्थित+धीः मुनिः उच्यते 

In sorrow, un-agitated mind, in happiness, (his) desires are gone, gone is passion/liking, anger, fear; He whose mind is steady, is called muni.

 √स्पृह् to desire intensely, long for 

2:57 He who is without attachment on all sides, encountering this or that, pleasant or unpleasant, neither rejoicing nor disliking, his Wisdom stands firm.

यः सर्वत्रानभिस्नेहः तत्तत् प्राप्य शुभाशुभम् 

नाभिनन्दति न द्वेष्टि तस्य प्रज्ञया प्रतिष्ठिता 

Vigraha and anvaya is practically the same for this verse also

यः सर्वरत्र अनभिस्नेहः तत् तत् प्राप्य शुभ +अशुभम् 

न अभिनन्दति न द्वेष्टि तस्य प्रज्ञा प्रतिष्ठिता 

an+abhi+√snih un-im-passioned

2:58 And when he withdraws completely the senses from the objects of the senses, As a tortoise withdraws its limbs into its shell, his Wisdom stands firm.

यदा संहरते चायं कूर्मो Sङ्गानिव सर्वशः  

इन्द्रियाणि इन्द्रियार्थेभ्यः तस्य प्रज्ञया प्रतिष्ठिता

Vigraha:

यदा संहरते च अयम् कुर्मः अङ्गानि इव सर्वशः 

इन्द्रियाणि इन्द्रियार्थेभ्यः तस्य प्रज्ञा प्रथिष्ठिता 

Anvaya:

च कूर्मः इव सर्वशः यदा अयम् अङ्गानि संहरते    

इन्द्रियाणि इन्द्रियार्थेभ्यः (संहरते ) तस्य प्रज्ञा प्रथिष्ठिता 

And like a tortoise  (who) withdraws its limbs from every direction, he who (withdraws) his senses from (the) sense objects, his Wisdom stands firm.