This is a concept that you will probably become very familiar with if you undergo CBT. It can help to explain why we have certain thoughts, why we perform certain behaviours and how they can make us feel. Now I’m no psychologist (yet : P), but I’ll try to explain this concept in the most psychologisty way that I possibly can!

So I’m going to base my examples around OCD, but the CBT triangle isn’t just used for treating OCD. It can be used to help many other areas of mental health – depression, eating disorder behaviours, anxiety ect.
An example in which this concept could be used: (OCD)

(Thoughts) “There’s a big event tomorrow, everything must go to plan, but there’s a chance someone might get ill. I must stop this from happening, otherwise I’ll be such a bad person and to blame for letting something go wrong and possibly spoiling the event.”

(Feelings)
•Worried
•Anxious
•Scared
•Agitated

(Behaviours)
•Finding the nearest thing to be able to perform a ritual (counting) to decrease feelings of anxiety
•Possible increase in rituals throughout the day(s)
•Being over cautious of symptoms of illness from you and other people
•Avoiding social situations to prevent illness spreading to you or family members

(I did try and put this example in a triangle formation, but it completely failed…just keep in mind the photograph above) So as you can see from this example, the main fear is that someone might get ill for this big event that’s happening and the sufferer feels like it’s her duty to prevent that from happening. Otherwise she will feel like a bad person and that it’s all her fault.
This thought triggers of the feelings of anxiety and agitation.
Now to suppress theses feelings the sufferer will carry out behaviours to do so. That being ritualising and looking out for signs of illness that normally would’ve not bothered her.
Then if she doesn’t complete any of these rituals the thoughts come back and the vicious cycle starts again.

It doesn’t always have to go in that specific order though. That’s why they have arrows on both end!

Feelings can affect the thoughts, which can affect the behaviours and vice versa, vice versa, vice versa. When you see it in the diagram it makes a lot more sense!

Hopefully that was understandable! I didn’t really choose the best example for the diagram, but oh well. It was a lot more difficult to explain than I expected it to be. I have all the information inside my head, but then when it comes to getting them down in words it proved really difficult! (Not so psychologisty) but I’m hoping it was a little bit understandable. : )
Thank you for reading!
If you have any questions about this, feel free to ask. I’ll do my best to answer them.