My dear child, you are unaware that you were born not of my womb but of another woman. Therefore you should know that your attempt is doomed to failure. You are trying to fulfill a desire which is impossible to fulfill.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
बालोऽसि बत नात्मानमन्यस्त्रीगर्भसम्भृतम् । नूनं वेद भवान् यस्य दुर्लभेऽर्थे मनोरथः
bālo'si bata nātmānamanyastrīgarbhasambhṛtam | nūnaṃ veda bhavān yasya durlabhe'rthe manorathaḥ
SB 4.8.12