Parasites are foreign entities that feed off the hosts' energy. A parasite might live with its host for a short or long time. It depends on how the host manages the parasite.
Negative emotions are feelings that obscure and chip away at your true self, a self that is made of love and light. Anger, anxiety, despair, hatred and jealousy are like parasites.
Parasites eat away at the positive emotions till none are left. If unattended for too long, negative feelings fester and grow until the host believes the parasite IS them.
Parasites are persistent and difficult to eliminate. Thus, you need to persevere and remain vigilant in finding ways to reduce and eventually remove these negative emotions.
To do this, you need to face the parasite. Directly confront it. If you are afraid to confront them on your own, seek help.
Every time you confront them, you get to know them better. When you know your negative emotions better, you can find ways to reduce them. Over time, the negative emotions become less and less till there are none are left.