Someone who is wistful is rather sad because they want something and know that they cannot have it. I can't help feeling slightly wistful about the perks I'm giving up. thinking sadly about something you would like to have but cannot have, especially something that you used to have in the past (wistly (15-18 centuries), probably from whist (15-20 centuries); influenced by wishful)
full of longing or unfulfilled desire; "those wistful little ads that the lovelorn place in the classifieds