It’s hard to overstate the impact self-talk has on mental health. I work in the field and can tell you people who accept that they influence their own mood have much better outcomes than people who don’t. People on average really struggle to accept that they have any control over their own well-being, and many build their self-concepts around external factors making them a certain way, so there’s nothing to do but continue being that way. This is a super common mindset when it comes to depression in particular