好好 (hǎo hǎo) is a colloquial reduplicated word meaning either 'in good condition, well' (of health, state, or relationships) or 'thoroughly, carefully' (doing something with earnestness). It is more casual than 良好 (good, favorable) for the first sense and softer than 彻底 (thorough, complete), which implies a full change rather than careful attention.