As the Stoic philosopher and Roman emperor Marcus Aurelius noted many years ago, the world itself is nothing but change, and our life is really just what our thoughts make it to be. Insofar as we have control over our thoughts, we have control over our lives. We may not always be able to control the stimulus, but from the perspective of the Stoic we should seek to control the response.
This is not always easy. Words have meaning, events have consequences, and our internal dialogue does not always follow the path we might intend for it. Like a dog let off leash in a park, or a bear finding its way into a populated village while in search of food, our minds can at times follow their instincts to strange and unfamiliar places with little provocation.