Since its inception in the seventies, transdisciplinarity (TD) has evolved in different streams and approaches [1], [2], [3]. Particularly, a common classification distinguishes two types: 1) "Theoretical" TD, led by the work of Nicolescu [4]; 2) "Practical" TD, which corresponds to the "Zürich school" [5], [6]. Although this classification has been very useful to date in many ways [7], the TD research field has matured in such a way that it is now time to move beyond. Firstly, there are today many transdisciplinary approaches that do not fit so well with this Western centric typology, such as the idea of "Indigeneous TD" [8]. Second, I have suggested that it might be more fruitful now to reframe the debate, by considering TD as a discipline by itself and/or a "way of being" in tension [9]. As a discipline, TD corresponds to specific skills, methods, and theories for knowledge integration and implementation within the scope of problem-solving research projects [10]. When TD is instead considered as a way of being, by contrast, it extends far beyond the scope of research projects and can manifest ubiquitously in the researcher's life. In both cases, social engagement can be intense and practical outcomes tangible; there are also important overlaps between the two, particularly in terms of researchers' skills and attitude [9]. However, whereas TD as a discipline is rather a means by which scientists contribute to problem-solving, TD as a "way of being" can also be seen as a solution that must be enhanced in society at large [9]. The aim of this short Letter is to explore further, in other words, the implications for sustainability transformations of being transdisciplinary, in contrast to practicing transdisciplinarity (as a discipline). I will start by briefly describing the second (the discipline), and show that it reaches some limits when it becomes either very global or very personal. This will be useful to further explore the TD way of being in a second time, with a focus on its implications for personal engagement in sustainability transformations.Practicing transdisciplinarity (as a discipline) is typically an activity performed by professional academic researchers, in the context of research projects with stakeholders. The aim is to solve complex problems, generally at a local scale, and the TD process by itself lasts for a given period of time (corresponding