In this kind of "all or nothing" thinking, we conclude that something will always or never be true in the future, because our minds are filled with examples of when it was true in the past and present, rather than examples of when it was not true. Trying to be helpful, our brains enact a kind of mental filter that keeps us from recognizing the exceptions to our "always" or "never."
It takes work to find these exceptions, not because they're not there, but because we pay less attention to things that don't fit our expectations and explanations - the stories we have about who we are and what the world is like. Even so, it is possible and important to do so - important because the seeds of change are often sown in experiences that don't fit our problem-oriented expectations. Successful change is less about reinventing the wheel, and more about slowly expanding the exceptions until they become the rule, and problems become exceptions.
Therapists can help in the process of identifying exceptions both because therapists are outside observers, without the filter of prior expectations or assumptions shaping what they hear, and because therapists are trained to ask questions that help unearth hidden exceptions. Postmodern approaches to therapy (such as Narrative Therapy, and Solution-Focused Brief Therapy) focus the most on exceptions, because they assume that meaning is constructed (i.e. built by people), and can be deconstructed and reconstructed differently. However, even behaviorism utilizes exceptions, seeking to change behavior by reinforcing a preferred behavior when it occurs - basically, calling attention to the exception with a reward, in order to increase the likelihood of it happening again.
I believe that there is always (yes, I mean always) an exception to the problem - there is a time, place, or circumstance when it is less likely to occur, or less intense when it does occur. There are parts of our experience that do not make it into the problem-focused "always" and "never" stories. Finding these exceptions creates hope that change is possible, and suggests ways to go about it.
Where do you find exceptions, for yourself or in your clients?