I know that nouns behaving as modifiers should take the singular form. However, I sometimes have problems telling if certain exceptions are possible. In the example below:
"I feel trapped in a cycle of negative and unpleasant thoughts."
Would it be grammatical to write: "I feel trapped in a negative and unpleasant thoughtS cycle"? I want to emphasize the fact that more than one thought keeps (should I say "keep?") revolving in my head. I will appreciate your help, sorry if you find this question too silly.