Anything occurring negatively is done in a negative way. This can mean it’s harmful in some way, such as an insult that negatively affects your self-esteem, or negative in a scientific sense, like negatively charged particles.
If something brings you down, it affects you negatively. It’s the opposite of positively. If you view something negatively, you’re seeing it in a bad light. If you tell someone she’s your best friend and she reacts negatively, it’s time to meet some new people! Also, magnets have negative and positive charges, so you can speak of a negatively charged magnet.