心情 (xīn qíng) is your general mood or state of mind — the everyday word for how you feel (e.g., 心情好, 心情不好). Compared with 情绪 (qíng xù), which points to specific emotions (often stronger or more negative), 心情 is broader and more neutral. 心态 (xīn tài) is your overall mentality or attitude, not a temporary mood.