In any situation, we always have a choice over how we behave. We can try to choose to think constructively or we can think destructively. Consider it as though our thinking is either a tool (useful and empowering) or an obstacle (harmful and disempowering).
Once this concept is understood, it gives us the ability to positively change our lives. By thinking and behaving as constructively as possible, life can be constructed in the way that we want. Thinking and behaving in a destructive way, on the other hand, can make life worse.