We have all — normally when young — experienced bullying or other negative traumas. The Lord Buddha was supposed to have been protected from trauma and not allowed to see that people age and grow sick.
For some of us, these traumas may be too strong and make it impossible to enjoy true silence of the mind. Despite our best efforts, these traumas may keep our internal voice chattering away with no respite and because these chatterings are centred on traumas, they will always be negative.
The phrase Dark Night of the Soul originates with St John of the Cross as a Christian experience, but it seems appropriate here as the negativity experienced can weigh heavily for a long period and stop spiritual progress. If you are a monk, this is the time to visit your Abbot. If you are a lay practitioner, then we can offer two techniques which should help. The important thing to remember when trying these techniques is give them time. Changes in how you feel do not happen overnight.
The first technique to use is the Loving Kindness Meditation. Use it at least daily, and it will change the person you are. This meditation fosters calmness and empathy for others, and most importantly in this case, empathy for yourself. Change takes time, but this is a very powerful technique.
The second technique which can be used as well as Loving Kindness meditation is the Joy of Life method. This method can be used not only when mindful or meditating, but at other times to replace any negative thoughts as they arise. This method requires perseverance, as it takes time to gain skill at replacing a negative thought with a positive thought smoothly and quickly.
I hope these techniques help. Just remember that they take time and need to be repeated over and over. If they are not sufficient, then do not be ashamed to get professional help.
Good luck with your demons, may they be left behind as you move forward!