In the face of climate change and other environmental issues, all relevant stakeholders, including members of civil society, should participate in the transformation towards a sustainable future. The project ‘Simply make a change’ engaged citizens (n = 101), with the help of an entirely voluntary and individual commitment approach, in a sustainable behavior they had not carried out before (e.g., plastic-free shopping or vegan nutrition). With the help of two questionnaires and subsequent interviews, participants were asked about their experiences with the commitment. The high proportion of participants who voluntarily sustained their chosen activity after the one-week trial run (78%), their rich and differentiated comments, and the formation of competencies such as mindfulness, reflectivity, and feelings of responsibility indicate that the approach was meaningful. Participants would have preferred a longer trial and perceived restrictions in daily life by behaviors with high task-difficulty (vegan nutrition), but felt confident to try out other sustainable behaviors in the future. The present data indicate that a completely voluntary self-commitment can encourage citizens to try out a new behavior and might also lower the threshold for trying other sustainable behaviors. This might contribute, step by step, to a more sustainable society.