Acceptance and Change

I am reading about two kinds of therapeutic approaches which have been combined recently. One is simply called "Cognitive Behavior Therapy", and what it tries to do is show how we can change our habits by framing our thoughts and experiences in different ways. One of these kinds of therapies actually consists in identifying painful thoughts and then rationally discovering the distortions in those thoughts. I believe that quite some time ago, I had blogged about Albert Ellis, who was something of a pioneer in this area. The point is that this model takes the view that it's our thoughts that create our pathologies. If we could only find ways to balance our thoughts by substituting new ones, we would be happier, or even develop healthier ways of responding to challenges.
    The second kind of therapeutic approach is more 'acceptance based', and one example is precisely called Acceptance Commitment Therapy (ACT). Under this 'more recent' model, the aim is not to alter one's thoughts or even deal with the content of thoughts at all. Rather, it is to simply realize the space in which those thoughts arise and not to be identified with the thoughts at all. ACT has a lot in common with meditation! This approach suggests that the source of suffering often arises precisely because one gets caught up in the content of one's thoughts, rather than seeing that one does not need to relate to one's thoughts in any specific way. Even so-called "constructive thoughts" are considered tools to gain valued ends, rather than things to ruminate on. You can probably tell that ACT is close to the strategy of mindful, non-judgmental awareness, where the concern is more about how mind is relating to thoughts than the content of the thoughts.
   The question that came to my mind is: how does one know what to accept and what can be altered or changed? I think that only when one has cultivated calmness of mind that they can decide for themselves how to use their thoughts. CBT is still valuable in the sense that it seems to encourage people to actually write out their thoughts and see how they look on paper. I have yet to see an article which explores why 'writing something down' is so powerful, but in this case I suspect it's because it gives me the space to contemplate the value of that thought overall, rather than the content per se. Just like with any kind of writing, there is a maturing process where one starts to develop an ideal narrative of how one could respond to life. To go back to my earlier question: this way of changing one's outlook through examining thoughts can be powerful. But on the other hand, it's also useful to accept whatever comes to mind as is, because those thoughts are somewhat immaterial. It especially happens when we come across situations where nothing can change how saddening something is, like the loss of a loved one. In those cases, there is no way to 'rationally dispute' that the situation is distressing. But by looking at the thoughts themselves with acceptance, it turns out that every thought is a perfect thought: perfect in its own causal conditions and in its present state, and perfect in a state of impermanence.