Can people feel happy and sad at the same time?
D000293:Adolescent; D000328:Adult; D000339:Affect; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006240:Happiness; D006801:Humans; D008297:Male; D008875:Middle Aged; D011582:Psychological Theory; D013997:Time Factors