This talk offers an overview of work on digital wellbeing and mental health that I have done with my research group and external collaborators over the last several 10 years. It unpacks the topics such emotional memories, awareness, regulation and processing, illustrated with relevant design exemplars. This talk highlights my reflection on the ethical challenges regarding these personal technologies and in particular on their use to inform big data-based services. The talk concludes with a call for the importance of considering these ethical implications when designing personal mental health technologies.