Valmiki Ramayana Kishkindha Kanda Sarga 1 Shloka 50
Original Shlokaदृढं हि हृदये बुद्धिर्मम सम्परिवर्तते। नालं वर्तयितुं सीता साध्वी मद्विरहं गता।।4.1.50।।
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हृदये in the heart, मम to me, बुद्धिः intellect, दृढम् resolved, सम्परिवर्तते exist, मद्विरहम् seperated from me, गता with, साध्वी chaste lady, सीता Sita, वर्तयितुम् to sustain, नालम् no strength
'My mind makes me feel certain that Sita with her chastity might not be able to live separated from me.