If you are putting thoughts and words into your paper that are both original to you and are not things you’ve written before, then there is generally no need to cite them in your work.
Citation has a very specific purpose in a paper and it’s to draw attention to any content, whether it’s ideas, facts or words, that are not original to that paper and are not considered common knowledge. This includes both elements that you have written before in earlier papers and content from outside sources.
The reason for that is actually very simple: When you put your name on your paper, you’re basically saying “This is my original work, except for the parts specifically mentioned that are not.”
As such, anything that is not cited in your work is presumed to be yours.
This actually comes up regularly in cases of academic plagiarism. Many students wonder why they can be accused of plagiarism when they did not explicitly say they created the work. What they fail to realize or don’t understand is that, once a work carries your name, it’s presumed to be an original work by you.
As such, it’s important to think of your name appearing on the cover or at the top of your work as something of a citation line. Where a quote in the text indicates someone else’s words and an in-text citation indicates a thought or fact from an outside source, the name at the top of the paper indicates who wrote the rest of the work.
Thinking of citation from this standpoint, it becomes much more clear when, where and how you should cite. Basically, anything that you wrote specifically for this paper doesn’t need to be cited directly because you’ve already cited it in the beginning.
All of this being said, you do need to make sure that the the passage is truly original and that the information is either yours or is otherwise common knowledge.
Even if the thought is yours, it might benefit from finding a citation for it. For example, if you have any opinion that you believe, it can be bolstered by finding an expert that shares it or a study that backs it up.
While it’s poor research to work backwards and find sources that support your conclusions, if the thoughts are yours then you likely have sources that share those opinions that you can cite. In those cases, your paper and your writing will be stronger for those citations, plus it avoids any potential for plagiarism allegations.
Still, there are times that isn’t practical, such as when you’re describing things you did or thoughts that are entirely personal to you. In those cases, citation isn’t necessary or appropriate. If anything, it’s redundant.
Just remember, with everything you write in a classroom, the presumption is that the entire paper is your original work unless you clearly state otherwise. Use citations to point out the exceptions to that, not the passages that follow that rule.