 Impressions of reflection include desires, emotions, passions, and sentiments. They are essentially reactions or responses to ideas, which is why he calls them secondary. Your memories of last year’s sunburn are ideas, copies of the original impressions you had when the sunburn occurred. Recalling those ideas causes you to fear that you’ll get another sunburn this year, to hope that you won’t, and to want to take proper precautions to avoid overexposure to the sun.