If "thinking" affects feeling, and "feeling" affects thinking, then "why" does this not produce a never-ending circle?

… forever.

But in a sense it is a never-ending cycle. But it’s not

The thought-feeling loops you mentioned are real, even if they don’t last forever. They can be big problems and last for a long time or happen frequently. One of the main reasons people go to therapy and/or take psychedelics (as medicine) is to break out of these loops. Either the therapist or the drug intervenes, essentially shaking the snow-globe of the mind up, making its snow fall in different patterns.

People were exposed to measles at a Rochester Hills medical office, Oakland Co. warns - The Detroit News

angry feelings -> angry thoughts -> angry feelings -> angry thoughts

For the same reason perpetual-motion machines can’t work: the first and second laws of thermodynamics. Energy is lost from the system, and that energy can’t magically regenerate. Put colloquially, we exhaust ourselves after a while. Another way of looking at it is that, at some point, you get distracted or, worst-case scenario, fall asleep.

This can happen:

Hello,hope y'all doin good, i came to Quora to share my strange story , a very weird one , a story when luck smiled at me ,maybe u will enjoy it , let's begin,have fun... A year ago ,I was a real porn addicted(btw I was 18) ,but never had sex before, I don't have a gf I didn't try to find one even ,always thinking to go to find a sex worker but then I just don't , everyday watching different bodies getting fucked and everyday enjoying. One day, I was watching porn, a big ass lady with big boobs ,just after seeing her the image of my female cousin poped in my mind, (let's introduce her : she's 35 years old , very big ass , nice boobs ,not very big but nice,always wearing tight clothes , she's divorced ) and I thought of me fucking her ,I never had sexual desires for her but now I do days went by and when I met her I was so horny ,I couldn't stay with the family cz my penis was clearly erected , I realized this is my first time I get horny for one of my family ,it not illegal in my country.well to make a long story short( if u want details just text me I will tell u 😊),I decided to give her signs that I want to fuck her,finally I decided to have sex and with my cousin , I thought it is the best beggining for me, i started touching her when I came across her in a narrow place , make her feel my hard cock when we hug , I thought it will hard and I will be ashamed but no , I felt nothing and she said nothing , probably she thought it was by mistake,anyways, I decided then to talk with her about sex, waited for her to be alone in a room and talk with her, I confessed everything about me watching porn and addicted..etc,she said it's normal and u are growing up and u must have sex,well at that time I was like whaaat????? Well I didn't control myself and asked her for sex ( horny like I Ve never been before) she said that she will think Abt it ,2 weeka went by then she called me ,telling that she reserved a room in a hotel and we meet tonight ,we met,and bruuhh, sex is great , I mean, I had to find a pirstitue ,what I was waiting for to have such a feeling ????, I will never forget that night, I started kissing her she was kissing hard ,she misses sex so bad , she sucked my dick and swallowed my semen ,I felt I'm in a dream , then when fucked ,her ass was very big and the anus was open ,didn't struggle to get my hard cock inside it , she was obviously missing sex , she was shouting ,fuck me yh fuck me , I go fast after every word until I cum , we did that 3 times , then we went to her pussy , using condoms I fucked her so hard the moans were higher , everything was perfect ,in the end I asked her to lick her body , licked pussy ,ass, boobs,then she sucked my cock until we sleeped ,all I know that she was dirty ,well before even having sex with her I knew she is an open minded woman , and a woman that looks that she donesnt know anything , but she knows everything, but never expected having sex with her ,well she was horny and that helped...but no one of us regretted that sex ever.. We still have sex from time to time ,and I started having sex with sex workers , joining threesomes..etc If u want pics of her text me.

What a feeling (and emotion) really is, is a body sensation plus a thought. So feelings themselves are partly made of thoughts. One way to see that this is true is to note that the body sensations of being anxious (e.g. about a big test coming up) and the body sensations of being excited (e.g. about an exciting movie) are almost identical. What makes them different feelings is a thought context, tagging them as bad and good, respectively.

Those realization thoughts could be anything that, in some way, changes the feelings. An example is a memory that pops up, in which the person you’re angry at gave you an amazing birthday present.

angry feelings -> angry thoughts -> angry feelings -> realization thoughts -> some other kind of feelings

Why were the Japanese soldiers in WW II so hesitant to surrender in battle?

Also consider an itch. It probably doesn’t trigger much of anything on its own—except maybe slight irritation. It’s just a body sensation. But try coupling that with the thought of “skin cancer.” Your state of mind will be very different, but the sensation will be the same.

E.g. the person you’re angry at suddenly drops his pants. Thought that might make you even angrier. Who knows? Still, eventually there will be some sort of distraction. (For some people, sadly, it’s alcohol or some other unhealthy or addictive thing.)

Because (sleep aside) this happens eventually:

Have you ever regretted not hitting on a older women?

Which is why so many therapies and meditation practices are about detaching thoughts from body sensations, learning to seem them as two separate things, rather than as a conglomeration.

angry feelings -> angry thoughts -> angry feelings -> distraction -> some different kind of thought or feeling.

All of the above is a toy version of human psychology. It’s not really a sequence of thought, feeling, thought, feeling, thought, feeling … It’s much more complex and messy than that, with thoughts and feelings intertwined. Plus, a thought can lead to another thought, instead of a feeling, and a feeling can lead to another feeling, instead of a thought. Or a feeling can lead to a thought and a feeling, etc.

Why are North Carolina Democrats against Mark Robinson? He is the modern Martin Luther King Jr. and the Democrats are being stupid for not voting him.

There’s a never-ending cycle (at least while we’re awake) of mental-event A causing mental-event B, causing mental-event-C and so on, but various realizations and distractions intrude, changing the course of the cycle. So it’s more of a chain than a cycle.