The phrase "ass in a sling" is a vulgar term used to describe a person who is in a difficult or uncomfortable situation. There are several antonyms that can be used to describe the opposite of someone with their "ass in a sling." These antonyms include: comfortable, relaxed, carefree, content, at ease, in control, well-off, and happy-go-lucky. People who fit these descriptions are typically not experiencing any major problems or struggles in their lives. They are able to navigate life with ease and are not overly stressed out or worried. While the phrase "ass in a sling" may be humorous or catchy, it is not a desirable situation to be in.