Bhagavad Gita · Chapter 18: Freedom through Renunciation

Bhagavad Gita 18.24

yattu kāmepsunā karma sāhaṅkāreṇa vā punaḥ | kriyate bahulāyāsaṃ tadrājasamudāhṛtam ||

But an action done by one who craves pleasure, or done out of egotism, and with a great deal of strain, is said to be of passion.

Modern context

Rajasic action is driven by desire or ego, and done with great strain. The last phrase is telling: bahulayasam, 'with much exhaustion'. Work done from craving or the need to prove oneself is tiring in a way that work done freely is not. Many people who burn out are not overworked so much as over-attached.