Can a self-kindness smartphone-app intervention increase self-esteem and reduce self-face avoidance in a visual probe paradigm?

The study has a repeated measures design (pre- and post-intervention) in which participants are randomly assigned to one of two groups (self-statement intervention or control intervention: relaxation exercises), resulting in a 2x2 design. Both groups answer pre- and post-intervention questionnaires on self-perception [self-esteem (RSES), narcissism (NPI)], questionnaires on well-being [depression (BSI-18), loneliness (UCLA)] and perform a reaction time task to assess visual attention to one's own face (modified dot-probe task). Self-statement group: over the course of a week, a self-statement is repeated via a smartphone app (auditory instruction). Each day, at least one self-selected self-statement (out of 10 self-statements) is to be repeated. Control group: Over one week, a relaxation exercise is repeated via a smartphone app (auditory instruction). Every day, at least one exercise (from a choice of 10) is to be performed.