"Heart Ain't a Brain" by Chris Brown explores the complexity of emotions in relationships. The lyrics reflect the struggle between what the heart feels and what the mind knows, emphasizing that love isn't always logical. Despite knowing that a breakup may be necessary, the heart still holds onto feelings of love, causing inner turmoil and confusion. The song captures the battle between rationality and emotions when it comes to love and heartbreak, ultimately highlighting the challenges of navigating relationships.