Getting positive actions/results from negative thoughts

I am trying to better understand how to explain to others and myself that negative thoughts always cause negative actions. I know that “negative” is relative but hopefully it is clear what I’m referring to.

Here’s an example model I’m trying to work through –
C – I have a goal to lose 20 pounds
T – I am not trying hard enough
F – Failure (I’m not sure if this can count as a feeling instead of a thought but it feels like a feeling in my body – maybe there’s a better word for it?)
A – Try harder, eat according to my plan, workout
R – I work harder toward my goal

This model doesn’t make sense because my R doesn’t prove the T true. I am trying to explain to myself that I must have another thought in there that is creating a positive result rather than a negative one – but then the result doesn’t hold. Did I temporarily manage to change my thought unconsciously to create the good result? How do I justify why the result is only temporary? It feels like trying harder is a result of thinking that I’m not trying hard enough and I’m trying to get a deeper understanding of what’s actually happening.