A thought is your brain throwing up because it received a stiimulus (either from within its own positive feedback loops or from without).
If everything was always agreeable, we wouldn’t have to have any thoughts at all.
I think it starts off as an emotional response for the briefest of semi-conscious moments, which pulls in bits and pieces of concepts to explain the emotion felt to the person, which results in a cohesive thought, all within probably a 1/4 second or so, maybe a little less.
This results in a quick story about “what just happened?” that’s reasonable and logical and cohesive, and we call the “what just happened?” the present moment.
CogPsych is making headway in that area, but they have a way to go but thankfully we have many thousands of years of great human knowledge to build upon already and most importantly, our own intuitions, thoughts, feelings, experiences to draw from, which are the most valuable of all.