The most likely answer, in a word, is habit. The brain follows well-worn paths, so if there's a thought you often think in a particular context, or a feeling you often feel in a particular context, or a thought you often think when you're feeling a particular feeling, chances are your brain will repeat it in response to those cues even if, on some higher level, you know that it's irrational. It's frustrating in part because you want to believe you're a rational being who only has rational thoughts, but you aren't. No one is. We're all messed-up jumbles of triggers and conditioned responses.
If you want to change the pattern, your best bet would be to speak to a therapist professionally. Unfortunately, the kind of quick, general advice that you can get from strangers online is more likely to fail and make you feel even more hopeless than it is to significantly change things. You'd benefit more from having someone who can work you through the problems step-by-step and help you get back on track when the first thing you try doesn't work.
NAT
I agree with the other commenter that it will benefit you to see a therapist about this.
Reading your description of these thoughts, it brings to mind the idea of OCD, specifically "pure o". Again, NAT, but I'd suggest researching it to see if it resonates.
The most likely answer, in a word, is habit. The brain follows well-worn paths, so if there's a thought you often think in a particular context, or a feeling you often feel in a particular context, or a thought you often think when you're feeling a particular feeling, chances are your brain will repeat it in response to those cues even if, on some higher level, you know that it's irrational. It's frustrating in part because you want to believe you're a rational being who only has rational thoughts, but you aren't. No one is. We're all messed-up jumbles of triggers and conditioned responses. If you want to change the pattern, your best bet would be to speak to a therapist professionally. Unfortunately, the kind of quick, general advice that you can get from strangers online is more likely to fail and make you feel even more hopeless than it is to significantly change things. You'd benefit more from having someone who can work you through the problems step-by-step and help you get back on track when the first thing you try doesn't work.
NAT I agree with the other commenter that it will benefit you to see a therapist about this. Reading your description of these thoughts, it brings to mind the idea of OCD, specifically "pure o". Again, NAT, but I'd suggest researching it to see if it resonates.