The researchers, from the University of Waterloo and the University of New Brunswick, asked people with high and low self-esteem to say "I am a lovable person."

They then measured the participants’ moods and their feelings about themselves. In the low self-esteem group, those who repeated the mantra felt worse afterwards compared with others who did not. However people with high self-esteem felt better after repeating the positive self-statement – but only slightly.

The psychologists then asked the study participants to list negative and positive thoughts about themselves. They found that, paradoxically, those with low self-esteem were in a better mood when they were allowed to have negative thoughts than when they were asked to focus exclusively on affirmative thoughts.

Writing in the journal, the researchers suggest that, like overly positive praise, unreasonably positive self-statements, such as "I accept myself completely," can provoke contradictory thoughts in individuals with low self-esteem. Such negative thoughts can overwhelm the positive thoughts.

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