Happiness is overcome by sorrow, and sorrow by pleasure. Some people while afflicted by sorrow, wish to recall (past) happiness, while others, while in the enjoyment of happiness, wish to recall past sorrow.
हर्षेण बाध्यते शोको हर्षः शोकेन बाध्यते। कश्चिद् दुःखे वर्तमानः सुखस्य स्मर्तुमिच्छति। कश्चित् सुखे वर्तमानो दुःखस्य स्मर्तुमिच्छति॥