There are often several reasons for the high repetition rate of your own papers. The first is that your topic is hot, so naturally a lot of content has been written by others, and it is easy to find duplication. The second is the website you choose. Hownet generally compares thirteen words. Once the similarity exceeds 80%, it is judged as a whole sentence. And your major. Some papers have a lot of technical terms, even if they are written by themselves, the repetition rate will be higher.