Study a single sutra by selecting the pada (chapter) and then the sutra (verse).
Source: English translation from The Yoga Sutras of Patanjali (Sri Swami Satchidananda)
To one of discrimination, everything is painful indeed, due to its consequences: the anxiety and fear over losing what is gained; the resulting impressions left in the mind to create renewed cravings; and the constant conflict among the three gunas, which control the mind.
Source: English translation from Light on the Yoga Sutras of Patanjali (B.K.S. Iyengar)
The wise man knows that owing to fluctuations, the qualities of nature, and subliminal impressions, even pleasant experiences are tinged with sorrow, and he keeps aloof from them.
Source: How to Know God: The Yoga Aphorisms of Patanjali (Swami Prabhavananda, Christopher Isherwood)
But the man of spiritual discrimination regards all these experiences as painful. For even the enjoyment of present pleasure is painful, since we already fear its loss. Past pleasure is painful because renewed cravings arise from the impressions it has left upon the mind. And how can any happiness be lasting if it depends only upon our moods? For these moods are constantly changing, as one or another of the ever-warring gunas seizes control of the mind.
Source: English translation from The Heart of Yoga (T.K.V. Desikachar)
Painful effects from any object or situation can be a result of one or more of the following: changes in the perceived object, the desire to repeat pleasurable experiences, and the strong effect of conditioning from the past. In addition, changes within the individual can be contributing factors.
Source: English translation of the Yoga Sutras of Patanjali (Swami Jnaneshvara Bharati)
A wise, discriminating person sees all worldly experiences as painful, because of reasoning that all these experiences lead to more consequences, anxiety, and deep habits (samskaras), as well as acting in opposition to the natural qualities.