A recent study in the APA journal Emotion reveals that when people lay on too much self-praise, it's detrimental to their growth and can lead to depression. Across several studies, it turned out that participants who ranked their performance higher than it should have been were more likely to feel depressed and dejected.
Co-author Chi-Yue Chiu notes that it likely has to do with the fact "inaccurate self-assessments can prevent self-improvement". It's certainly still important to pat yourself on the back now and again, but be weary of overdoing it and overlooking your faults, an idea French essayist Michel de Montaigne seems to peg on the above quote.
Too Much Undeserved Self-Praise Can Lead to Depression [Science Daily]