In response to a comment from Monica where she asks if thought forms once created may change, my experience this does not happen.  I perceive them as having the originator’s intent and thoughts imprinted upon them like a kind of programming which just keeps running, until either the originator or someone perceptive and powerful enough dissolves it.   

If we have hurt someone by sending  negative energy to them we can heal the effects by seeking mutual forgiveness, sending light and love for healing.  We can even call back the energy we sent and consciously undo the programming we created.  

It is rather humbling to know that we can at times unwittingly hurt others with just our thoughts.  I think the bottom line is to be aware of our intent, do we really and truly want to exact revenge or hurt someone?  Or are we just letting off steam.   In terms of our own path, when we are truly contrite (sorry) and we know we won’t repeat a misdeed.  In fact many people demonstrate their contrition by expressing compassion towards those they have hurt.  Remember that the Divine forgives us, but we also need to forgive ourselves in order to move forward and be a better person in the future.