न कर्म निष्फलं कुर्यान् नायत्यामसुखोदयम् ।
na karma niṣphalaṁ kuryān nāyatyām asukhodayam |
(Manu Smṛti: 4.70; cited in Amṛta-ṭīkā to Hari-nāmāmṛta-vyākaraṇam: Maṅgalācaraṇa, 1)
“One should perform neither an action that is useless [i.e, has no purpose and will prove fruitless] nor one that gives rise to unhappiness in the future.”