ध्यायतो विषयान्पुंसः सङ्गस्तेषूपजायते। सङ्गात् संजायते कामः कामात्क्रोधोऽभिजायते ॥

dhyāyato viṣhayān puṁsaḥ saṅgas teṣhūpajāyate saṅgāt sañjāyate kāmaḥ kāmāt krodho ’bhijāyate

Man, musing on the objects of sense, conceiveth an attachment to these; from attachment ariseth desire; from desire anger cometh forth;

In plain words: When a person keeps thinking about things they enjoy, they start to get attached to them. Attachment turns into wanting, and when the wanting is blocked, anger comes.