In human-centred design (HCD), researchers and designers attempt to cooperate with and learn from potential users of the products or services which they are developing. Their goal is to develop products or services that match users' practices, needs and preferences. In this position paper it is argued that HCD practitioners need to deal with two tensions that are inherent in HCD: they need to combine and balance users' knowledge and ideas with their own knowledge and ideas; and they need to combine and balance a concern for understanding current or past practices with a concern for envisioning alternative or future practices. Six HCD approaches - participatory design, ethnography, the lead user approach, contextual design, codesign and empathic design - are discussed in order to argue that these different approaches are different ways to cope with the two tensions. In addition, several examples from practice are provided to illustrate these tensions. Moreover, it is advocated that HCD practitioners critically reflect on their practices, their methods and their own involvement, so that they can more consciously follow specific HCD approaches and more mindfully cope with the two tensions.