The theologian Paul Tillich characterized existential anxiety as "the state in which a being is aware of its possible nonbeing" and he listed three categories for the nonbeing and resulting anxiety: ontic (fate and death), moral (guilt and condemnation), and spiritual (emptiness and meaninglessness). According to Tillich, the last of these three types of existential anxiety, i.e. spiritual anxiety, is predominant in modern times while the others were predominant in earlier periods. Tillich argues that this anxiety can be accepted as part of the human condition or it can be resisted but with negative consequences. In its pathological form, spiritual anxiety may tend to "drive the person toward the creation of certitude in systems of meaning which are supported by tradition and authority" even though such "undoubted certitude is not built on the rock of reality".
Butterflies in your stomach before an important event? Worried about how you will meet a deadline? Nervous about a medical or dental procedure? If so, you are like most people, for whom some worry about major events (like having a child, taking an exam, or buying a house), and/or practical issues (like money or health conditions), is a normal part of life. Similarly, it is not uncommon to have fears about certain things (like spiders, injections, or heights) that cause you to feel some fear, worry, and/or apprehension. For example, many people get startled and feel nervous when they see a snake or a large insect. People can differ in what causes them to feel anxious, but almost everyone experiences some anxiety in the course of their life.
When we’re anxious, the body produces a stress response. The stress response is designed to give us an extra ‘boost’ of awareness and energy when we think we could be in danger. The stress response causes a number of physiological, psychological, and emotional changes in the body that enhance the body’s ability to deal with a perceived threat – to either fight or flee, which is the reason the stress response is often referred to as the ‘fight or flight response.’