Losing sleep over something can be a difficult and stressful experience. The crossword solutions for the term 'lose sleep (over)' are OBSESS (6 letters), FRET (4 letters), AGONIZE (7 letters), STEW (4 letters), and WORRY (5 letters). All of these words describe the feeling of being preoccupied with a certain issue or problem, often to the point of being unable to focus on anything else. This can lead to a lack of sleep, as the person is constantly worrying and thinking about the issue.