Worry is thoughts, images and emotions of a negative nature

Pessimism

Pessimism, from the Latin word pessimus , is a state of mind in which one perceives life negatively. Value judgments may vary dramatically between individuals, even when judgments of fact are undisputed. The most common example of this phenomenon is the "Is the glass half empty or half full?"...

 in which
mental attempts are made to avoid anticipated potential threats. As an emotion

Emotion

Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...

 it is experienced as anxiety

Anxiety

Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...

 or concern about a real or imagined issue, usually personal issues such as health or finances or broader ones such as environmental pollution and social or technological change. Most people experience short-lived periods of worry in their lives without incident; indeed, a moderate amount of worrying may even have positive effects, if it prompts people to take precautions (e.g., fastening their seat belt

Seat belt

A seat belt or seatbelt, sometimes called a safety belt, is a safety harness designed to secure the occupant of a vehicle against harmful movement that may result from a collision or a sudden stop...

 or buying fire insurance) or avoid risk

Risk

Risk is the potential that a chosen action or activity will lead to a loss . The notion implies that a choice having an influence on the outcome exists . Potential losses themselves may also be called "risks"...

y behaviours (e.g., angering dangerous animals, or binge drinking).

Excessive worry is the main component of generalized anxiety disorder.
One theory of anxiety by Liebert and Morris in 1967 suggests that anxiety

Anxiety

Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...

 consists of two components; worry and emotionality.