Emotions are a vital part of people's life and mental health. Facilitating proper emotion regulation (ER) is important for an individual's well-being, aiming to maximise satisfaction or minimise discomfort. While how to effectively design an emotion regulation tool, which helps individuals to change their emotions from negative to positive ones in-the-moment emotional need, is still an open challenge without good design-for-emotion regulation guidelines. Thus, exploring general and feasible design principles for designing smart emotion regulation tools is needed. In this study, we firstly propose a design-for-emotion regulation framework for Arts and Design university students based on personality-supported emotion regulation strategies. Secondly, we identify daily scenarios that could cause negative emotions in university students based on a focus group study with design thinking methods, and then interpret the related emotion regulation strategies into specific design tactics (principles). Thirdly, we conduct a questionnaire survey (N=65) of university students to confirm and enrich typical real-life scenarios causing negative emotions and further refine ER tool design principles. Finally, we discuss the future research on smart ER system design is presented, including personality-supported ER material design and technology-based interaction design for personalised emotion regulation.