In the last decade, an increasing amount of people has become aware of the negative impact their behaviour has on the environment. However, most consumers are not aware of the negative environmental impact of the products they purchase and possess. Research has been done on different aspects of products for a circular economy, such as product longevity, and on the purchase process but mostly for marketing reasons instead of sustainability. Research has also been done on the gap between intention and behaviour of sustainability minded people. This research presents barriers, but no research was found on translating these barriers into solutions. Little was found in literature about making appropriate sustainable buying decisions. The main objective of this thesis is to stimulate consumers to exclusively purchase products with long-term psychological value, with the ultimate goal of reducing the ecological footprint of the consumers. In the first part of this research the characteristics of personal long-term value of products are identified. Data for this study is obtained through ten in-depth interviews and literature review. The second part of this research aims to identify how the purchase behaviour could be changed and which factors influence the purchase behaviour. This part contains a literature review and utilises the research through design method, in which five different prototypes are tested. The third part of this thesis translates this new theory into practice. Three new prototypes are developed, which should together affect the change in purchase behaviour. These products are validated with five participants over three weeks. The results of the interviews show three categories of psychological long-term product value: products that carry memories, products that satisfy basic needs and products which enable human goals. These last two categories complement each other. The research on behavioural change shows that the human goals should be discovered first, which results in a personal set of long-term product values. Next, consumers have to be reminded of their values during the purchase process. Finally, sufficient commitment should be created to resist the products that do not fit the personal set of long-term product values. For this, a game is proposed to raise awareness and discover this personal set of long-term product values. This game enables the consumer to train the reasoning behind the desire for products. The validation test showed that the game is successful in creating awareness and in training consumers to reason about products with personal long-term product value. To make the consumer remember their set of personal long-term product values in the purchase process, two reminders are proposed: the ‘Product Calendar’, and a sticker set ‘Stick to your values’. These designs remind the consumer of their long-term product values, translate the game into real life and create commitment. In conclusion, this project enables designers to understand long-term psychological product value, gives them a framework to design for purchase behavioural change, and the designs of this project enable consumers to make more sustainable purchase decisions.