Motivational and affective aspects have long been neglected in research and development of technology enhanced learning (TEL) solutions, but it is now increasingly recognized that they are key to acceptance and sustainable success. However, the consideration of these aspects still suffers from fragmented research activities that are in between established disciplines. We summarize the results from three editions of the EC-TEL workshop series MATEL, which has established a forum for interdisciplinary conversations and joint re-search activities. This includes an overview and systematization of current re-search and its findings as well as prioritized research challenges. The paper concludes with a research agenda that advances the inclusion of motivational and affective aspects into TEL from art to an engineering approach.