The characters combine literally and powerfully: “Left [and] right become difficult.” This structure makes the idiom incredibly intuitive. The moment you hear it, you can visualize someone looking left and right, finding no easy way out.
In Chinese culture, where social harmony (和谐, héxié) and interpersonal relationships (关系, guānxi) are highly valued, 左右为难 often arises from conflicting loyalties or obligations. The dilemma is frequently not just about personal gain or loss, but about how a decision will impact one's family, friends, or colleagues. Making a choice that disappoints a parent to please a spouse, or siding with one friend in an argument against another, are classic 左右为难 scenarios. A useful comparison is to the English phrase “caught between a rock and a hard place.” While the meaning is nearly identical (a choice between two bad options), the cultural *flavor* can differ. In a Western context, the “rock” and “hard place” might more often be financial, legal, or personal career choices. In a Chinese context, they are very frequently social or relational obligations. The pain of the dilemma often comes from the fear of disrupting harmony or failing in one's duty to others, which can feel more acute than in more individualistic cultures.
左右为难 is a very common idiom used in both formal and informal contexts. It's sophisticated enough for a business report but common enough for a casual chat with friends.