What are the principles that underlie assessment of non-pecuniary damages?

A concise, helpful summary of the principles that underlie assessment of non-pecuniary damages is found in In Peterson v. Verma, 2014 BCSC 2622, where Dickson J. (as she then was) stated:

Non‑pecuniary damages are awarded to compensate a plaintiff for pain, suffering, loss of enjoyment of life and loss of amenities. The compensation awarded should be fair to all parties. Fairness is measured against awards made in comparable cases which, though helpful, serve only as a rough guide to appropriate compensation. Each case depends on its own unique facts: Trites v. Penner, 2010 BCSC 882.

The list of common factors for consideration when assessing non‑pecuniary damages includes the age of the plaintiff, the nature of the injury, the severity and duration of pain, disability, emotional suffering, loss or impairment of life, impairment of family, marital, and social relationships, impairment of physical and mental abilities, loss of lifestyle, and the plaintiff's stoicism which, as a factor, should not, generally speaking, penalize the plaintiff: Stapley v. Hejslet, 2006 BCCA 34.

The assessment of non‑pecuniary damages is influenced by the plaintiff's personal experiences in dealing with his or her injuries and their consequences. A functional approach should be adopted. A clear appreciation of the individual plaintiff's loss and need for reasonable solace is the key: Dilello v. Montgomery, 2005 BCCA 56; Dikey v. Samieian, 2008 BCSC 604.