 Participants will be randomly assigned to one of three groups: 1 DM, 2 CR, and 3 a waitlist control group. The waitlist control group will wait for two weeks i.e., as long as the intervention in the other two groups last, before participants will be once more randomly assigned to one of the two active conditions DM and CR, which they will then regularly participate in. Thus, all participants enrolled in the study receive one of the two treatments sooner or later. For participants who are initially assigned to the waitlist group, there will be a second pre-assessment prior to the start of the intervention. 