Denial is the refusal to accept reality or fact, acting as if a painful event, thought or feeling did not exist. It is characteristic of early childhood development. Many people use denial to avoid dealing with painful feelings or areas of their life they don’t wish to face.

Regression

Regression is the return to an earlier stage of development in the face of unacceptable thoughts or impulses. 

Acting Out

Acting out is performing an extreme behaviour in order to express thoughts or feelings the person feels incapable of otherwise expressing. The behaviours will usually be considered bad or antisocial and are generally destructive to either the self or to others. Feelings are translated into actions rather than being felt. It is an unconscious process.

In acting out as defined by Freud, his patients were acting out when they could not access their repressed memories that were motivating their unconscious behaviours and they “symbolically dramatised the past in order not to remember it”. 

Dissociation

People who have a history of any kind of childhood abuse often suffer from some form of dissociation.

https://childrenofnarcissists.org.uk/trauma-and-dissociation/

Compartmentalization

Compartmentalization is a lesser form of dissociation, where parts of oneself are separated from awareness of other parts and behaving as if one had separate sets of values. This is the root of hypocrisy and cognitive dissonance.

Projection

Projection is the act of ascribing a person’s undesired thoughts, feelings, or impulses onto another person who does not have those thoughts, feelings or impulses.

Repression

Repression is the unconscious blocking of unacceptable thoughts, feelings and impulses. 

Displacement

Displacement is the redirecting of thoughts feelings and impulses directed at one person or object, but taken out upon another person or object.

Intellectualisation

Intellectualisation is the overemphasis on thinking. A person might employ intellectualisation to distance themselves from an impulse, event or behaviour. 

Rationalisation

Rationalisation is putting something into a different light or offering a different explanation for one’s perceptions or behaviors in the face of a changing reality.

Mature Defences

The following defense mechanisms are more mature and are the most constructive and helpful, but may require practice and effort to put into daily use. People with mature defenses tend to be more at peace with themselves and those around them.

Sublimation

Sublimation is the channeling of unacceptable impulses, thoughts and emotions into more acceptable ones. Humour, when used as a defense mechanism, is the channeling of unacceptable impulses or thoughts into a light-hearted story or joke.

https://www.learning-mind.com/sublimation-in-psychology/

Compensation

Compensation is balancing perceived weaknesses by emphasising strength in other areas.

Assertiveness

An individual is successfully assertive when being clear in communication without the need to be aggressive and blunt. They express their opinions or needs in a respectful yet firm manner, and listen when they are being spoken to. Becoming more assertive is one of the most desired communication skills and helpful and mature defence mechanisms.