Welcome to the forum!

Do you mean instability of the dream itself? If so, I would advise checking out these pages on our Wiki about Dream Stability and Control.

Or do you mean emotional instability? It's fairly normal for emotions to be amplified in dreams, lucid and non-lucid. However, lucid dreams give you the perfect avenue for which to find out why your are having these intense feelings. If the characters in your dream are acting violent towards you, remind yourself that you are dreaming and cannot be hurt, and then confront them on why they are acting the way they are, or what they are supposed to represent. If instead you're the one feeling inexplicably violent in your dreams, set an intention during the day that you will remain calm when you are lucid, or set an intention that you will have peaceful lucid dreams. Either way, be prepared that the dream may show you some aspect of yourself that you may need to improve on in order to reduce these feelings of anger and violence.

Let us know if you have any other questions, and feel free to stop by the IRC chat.