The holocron of Darth Erebos, The fourth Entry.

The hologram's entry flickers to life Erebos sat on the throne from previous entries though none of the Tuk'ata were around him this time, instead he had his armor on and a faceless and eyeless facial plate simply seemed to stare at the viewer. "It is time to explain the source of my power, how to achieve the cold rage which fuels my power but allows me to remain as focused and clear headed as a razor." His voice was distorted and deeper than the previous entries but now he stopped as if pondering about weather or not he actually should reveal what he had learned and achieved. Then as if to scoff at himself he continued as simply as if he had never stopped in the first place.
"Inside every force user is a place, a clear place as briskly clean as ice on a mountain top, cool and remote. Find that high place and look down within yourself, breathe that clean icy air as you regard your emotions but above all do not deny them. Instead observe them, take your horror, fear, anger, your emotions and look at them, examine them as if they were a simple phenomenon, smell them, taste them, come to know them as only you can, for they are yours and they are precious."
Erebos paused as if to let those words digest in the air between him and the recording holocron. "The place should feel remotely frozen but at the same time as hotly intimate as anything you have ever felt, once you are there take your emotions, handle them, dissect them, pull them apart and resemble them. You should still feel them, if anything they should burn hotter than before but they should no longer have the power to cloud your mind. This should be your exercise as you meditate on the mantra of the sith, understanding it and this exercise is the key to unlocking cold rage. If you do not believe me then simply look at history, it's two most famous practitioners were in fact Count Dooku and Darth Sidious, one of which was and still is considered the most powerful and influential sith in the galaxies history."
Erebos moved his hands up, placing his finger tips against the same fingertip of the other hand and brought it up to the level of just bellow his chin. It was as if there was something he wanted to add. "The last part will be up to you to figure out how to find the... mountain top shall we call it, within yourself. That will be your own task, if I give away too much then you won't learn anything or grow on your own. That is for yourself to discover." He then opened his fingers and the hologram ended.