wistful

adj. yearningly pensive, dreamy with longing (especially for things past); melancholy, sad

(a.)
Longing; wishful; desirous.
  

(a.)
Full of thought; eagerly attentive; meditative; musing; pensive; contemplative.
  

Adjective
1. full of longing or unfulfilled desire; "those wistful little ads that the lovelorn place in the classifieds"
(synonym) yearning
(similar) sad
2. showing pensive sadness; "the sensitive and wistful response of a poet to the gentler phases of beauty"
(synonym) pensive
(similar) sad