A question in regards to applying the model to a feeling.

One of the frequent feelings I have, is that of tiredness.
If I am feeling tired, how does that fit in the model?
I am attributing my tiredness to work, long hours, work related stress etc. What thought am I having that is making me feel tired- why I am not just tired?

…or is my tiredness just a circumstance, and it’s the way I think about it i.e using it as an excuse not do things, the issue?

I would really appreciate your view on this.