There are several negative consequences of plagiarism in your paper.
First of all, plagiarism in your work would affect your reputation. Even if that was a one-time failure, you still would be suspected till the end of your studies. All the schools, universities and colleges do take plagiarism issues very seriously. So, if you were caught once, do not hope it would be forgotten one day. It impacts your reputation as a student.
Plagiarism destroys the academic career. Once detected, it goes out and is widely reported in the academic world. Usually, this report means none of your further works would ever be accepted for publish. Such a situation leads to an inevitable end of an academic career.
Apart from influencing your personal and academic reputation, plagiarism also affects the person you stole from. Think of it from the side of that person. What if your research was stolen? You’ve spent a lot of time (and probably money too!) to find relevant info, analyze it and complete it in the text form. How would you feel if someone would simply take it and present as own?
Even though plagiarism is often taken not that serious, it might also lead to legal issues. Moreover, they are not rare. The law here is absolute. You can’t use the work of another person without proper citations and references. Otherwise, it can lead to a law sue, criminal offense or even prison.