Loneliness adds beauty to life. It puts a special burn on sunsets and makes night air smell better.
An explanation for Loneliness adds beauty to life
In this quote, Henry wants to emphasize the importance of loneliness. When a lonely person sits on the seaside and looks upon sunset, he internally feels the heat and thinks about the moments when his loneliness was not there. Beauty is intrinsic of an animal, thought, object, human or place that provides a cognitive feel of pleasure or satisfaction.
Loneliness is a complex and usually unpleasant emotional response to isolation. Loneliness typically includes anxious feelings about a lack of connection or communication with other beings, both in the present and extending into the future. As such, loneliness can be felt even when surrounded by other people. (Wikipedia)
Henry says that to feel such feelings you need to put your heart and mind on the sunset scene. Which is just before you where you are sitting. When you are sitting before the scene you need to be relaxed and feel the feeling.
In order to succeed in such scene settings, one must have a heart of feeling. A heart that feels the moments of life.