Valmiki Ramayana Ayodhya Kanda Sarga 8 Shloka 17
Original Shlokaसा त्वमभ्युदये प्राप्ते वर्तमाने च मन्थरे। भविष्यति च कल्याणे किमर्थं परितप्यसे।।2.8.17।।
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मन्थरे O Manthara, सा त्वम् you, अभ्युदये prosperity, प्राप्ते affained, वर्तमाने च at present, कल्याणे wellbeing, भविष्यति will have in future, किमर्थम् why, परितप्यसे are you grieving.
Manthara, we have enjoyed prosperity in the past, we are enjoying it now and we will enjoy it in future. Then why are you aggrieved?