I felt that this article (including the published academic article that is cited) is written as if we have a lot of control about what we think. Studies in neuroscience have shown that thinking happens automatically. Additionally, studies in mindfulness meditation have shown that we can be aware of our changing thoughts and also that we can gradually train our minds to not get entangled in worrying, regretting and other mental proliferations – avoiding these types of mental phenomena are important in order to avoid  mental health problems (regardless of whether one is old or young).