A sentencing court misdirects itself when it overemphasizes aggravating features of an offence to the exclusion of or without giving sufficient weight to clear mitigating factors. While armed robbery is a serious offence warranting imprisonment due to its nature involving premeditation, use of force, and violation of personal security, the sentence must be proportionate and balanced. Mitigating factors including youthfulness, first offender status, guilty pleas, cooperation with authorities, recovery of stolen property, and ability to make restitution must be given meaningful weight and not merely lip service. A guilty plea must be recognized and rewarded as a valuable contribution to the effective and efficient administration of justice. The court must impose the minimum effective sentence necessary to serve the interests of justice, as very long sentences have diminishing marginal deterrent value. An appellate court may interfere with a sentence that is "disturbingly inappropriate" due to such misdirection.