Stress significantly impacts emotional well-being, leading to conditions such as anxiety, depression, and burnout. While breathing exercises have been shown to alleviate stress, there is a lack of research involving users in the design of tools that visualise emotions and provide personalised, real-time stress relief. This study addresses that gap by developing and evaluating a personalised mobile app designed to visualise users’ emotions and deliver tailored breathing exercises to reduce stress. The study integrates psychological theory through the Plutchik Model with personalised breathing techniques, aiming to enhance emotional awareness, engagement, and well-being, aligning with Sustainable Development Goal 3. A user-centered design approach was critical, involving users aged 18 to 30, who often experience high stress levels, throughout the design and development process. This ensured the app was tailored to their needs. Usability testing showed a significant increase in user satisfaction and stress reduction, with customisable breathing exercises proving highly effective. The app’s ability to track emotional states and provide real-time stress-relief interventions offered substantial benefits for users’ mental health. Further refinement of the emotion classification algorithm and the integration of emerging technologies like AI, AR, and VR could enhance the user experience and emotional management, contributing to better emotional literacy and stress reduction.