Generally Behavioral changes before mental illness arises often have some warning signs, such as:

• Anorexic
• Have negative thoughts about themselves
• Feeling often anxious or troubled
• Feel very hopeless or depressed
• Feeling more paranoid, suspicious, or anxious about the things around you
• Anger or mood swings
• Distracted
• Not as happy with life as before
• There is a feeling that living each day is difficult.
• Often new thoughts or strange feelings arise, or may not feel at all.
• Sleeping too much or having trouble sleeping
• Not self care and cleanliness
• Difficulty separating imagination and reality 
• Confused speech or have communication problems
• Separating from society or spending more time with oneself
• Have worsening academic or work performance problems

However, if you find yourself continuing these behaviors or the behavior is violent. Should see a doctor for examination and appropriate treatment plan. Because of how quickly the problems related to mental health are treated? The chances of being healed will also be high.