Let us first explore the some terms related to our "emotional world" and what it means. This is emotional literacy, and it is very important for us to learn in order to solve emotional problems. Just like learning numbers and numeracy to solve math problems, we need to learn emotional literacy in order to effectively solve emotional problems.
The human mind has a great ability to fuse, hook into, or buy into a story whether that story may be in a form of a movie, story book, or thoughts in one's head. So when one is feeling sad, upset, happy, or angry, one may have fusion with a story in one's head.
So how can we change this?
We simple have 2 main options. One is to change our story. The other option is to unhook, detach, step back, or defuse from that story. Traditionally, cognitive behavioural therapy (CBT) is more about understanding the story and helping a person to change that story into a more "positive" or helpful one. Acceptance Commitment Therapy (ACT), is more about coaching a person to defuse or unhook from that story, and once unhooked, the story will natural has less grip on that person.
There are therapists who consider defusion or unhooking from thoughts a better strategy, and at the same time, I personally believe that thought defusion and thought challenge needs to go hand and hand. Having said that, I do believe that if one is very fused with one's thoughts, it is much harder to do thought challenge effectively. That is to say that one has to defuse from thought first in order for thought challenge to be more effective.
At a pragmatic level, if one is very fused with thoughts, I would lean towards a more ACT approach. If one is already defused or detached from thoughts, I may take a more CBT approach. I personally think that there is a lot of overlap between these two modalities in any case.