Trials design. This study will include two parallel-randomized trials, with pre-post measurements. The designs of the trials will be similar and compliant with the CONSORT guidelines. In the first trial the efficacy of the preventative version of the application will be tested against a wait list control group, in a healthy sample of participants. In the second trial the efficacy of the app will be tested against a wait list control group, in a sample of participants with mild depressive symptoms.