These characters combine to create a powerful metaphor. Someone with a “small heart-eye” has a limited capacity for generosity (`小心`) and a narrow perspective (`小眼`). They are unable to see the bigger picture and get bogged down by insignificant slights or costs.
In Chinese culture, generosity, magnanimity, and the ability to maintain social harmony are highly prized virtues. The concepts of `大气 (dàqì)` (magnanimous, broad-minded) and `大方 (dàfāng)` (generous) describe an ideal personality type—someone who is forgiving, not calculative, and socially smooth. `小心眼` is the direct cultural antithesis to this ideal. To call someone `小心眼` is a significant social criticism. It implies they are difficult to get along with, create friction over unimportant issues, and lack the social grace to “let things go.” A helpful Western comparison is the term “petty” or “thin-skinned,” but `小心眼` is broader. While an American might call someone “petty” for getting upset about a small comment, `小心眼` also strongly implies being stingy or ungenerous. For example, a friend who insists on splitting a tiny bill down to the last cent could be described as `小心眼`, a connotation less present in the English word “petty.” It's a fundamental criticism of one's character and generosity of spirit.
`小心眼` is a very common, informal term used to complain about or describe people in everyday life. It is almost always negative and is considered an insult, though its severity can range from a mild complaint to a serious character judgment.