Self-awareness is the noun: knowing and understanding what you yourself are like — your habits, your feelings as they happen, your strong points, your weak ones, and the effect you have on other people. It is uncountable, so you say 'a lot of self-awareness' or 'a lack of self-awareness', not 'a self-awareness'. The word lives in two places. In everyday talk about people, it is a quality you praise: 'She has real self-awareness — she knows how she sounds when she's tired.' In psychology and in schools it is a skill people can learn and practise, often listed next to things like empathy and self-control. English also uses it in a dry, funny way in the negative: 'the complete lack of self-awareness' of someone who complains that other people talk too much. It is a fairly formal word, more written than spoken; in ordinary conversation people often just say 'he knows himself well' or 'she knows what she's like'.