entering the river of misery

I’m new to scholars and thrilled to be here. On the weight loss material you talk about going off sugar and flour as entering the river of misery in terms of withdrawal symptoms, etc. I was encouraged by the truth that there is withdrawal from these substances and there’s a period of “feeling worse” to get through before feeling better. I am onboard with moving through the pain in exchange for the freedom that is on the other side. The place I feel some confusion is about thoughts. You often talk about “choosing the thought that serves you.” I assume that choosing the thought “It will be easy for me.” is a misunderstanding of your work. Another way of asking the question would be “Is ‘I’m entering the river of misery.’ a circumstance or is it a thought. How do you distinguish between circumstances and thoughts? Thank you!