High Self Esteem is what i would consider not as bad as low self esteem. Usually those with high self esteem are not prevalent with depression or mental disorder's but at some points are more prone to narcissism and more impulsive behaviors.
Low Self Esteem is usually way more dangerous, with subjects not holding themselves in high regard. They may not value their life as much and are prone to self destructive behaviors, depression, anxiety, eating disorders, and suicidal/homicidal ideation.