People have different ways of handling their anxiety and pain.  Originally conceived by Sigmund Freud, much of the development of the concept of defense mechanisms was done by his daughter, Anna Freud. Defense mechanisms can be healthy or unhealthy depending on the circumstances and how much a person uses them. They can hide many different feelings from anger to lust to guilt. Here are a list of some common defense mechanisms from:  http://www.utahpsych.org/defensemechanisms.htm:

Repression

Burying a painful feeling or thought from your awareness though it may resurface in symbolic form. 

You can't remember your father's funeral.

Denial

Not accepting reality because it is too painful.

You are arrested for drunk driving several times but don't believe you have a problem with alcohol.

Regression

Reverting to an older, less mature way of handling stresses and feelings

Projection

Attributing your own unacceptable thoughts or feelings to someone or something else

You get really mad at your husband but scream that he's the one mad at you.

Splitting

Everything in the world is seen as all good or all bad with nothing in between.

You think your best friend is absolutely worthless because he forgot a lunch date with you.

Isolation of affect

Attempting to avoid a painful thought or feeling by objectifying and emotionally detaching oneself from the feeling

Acting aloof and indifferent toward someone when you really dislike that person

Displacement

Channeling a feeling or thought from its actual source to something or someone else.

When you get mad at your sister, you break your drinking glass by throwing it against the wall.

Reaction Formation

Adopting beliefs, attitudes, and feelings contrary to what you really believe

When you say you're not angry when you really are.

Rationalization

Justifying one's behaviors and motivations by substituting "good", acceptable reasons for these real motivations

I always study hard for tests and I know a lot of people who cheat so it's not a big deal I cheated this time.

Altruism

Handling your own pain by helping others.

After your wife dies, you keep yourself busy by volunteering at your church.

Sublimation

Redirecting unacceptable, instinctual drives into personally and socially acceptable channels

Intense rage redirected in the form of participation in sports such as boxing or football

Suppression

The effort to hide and control unacceptable thoughts or feelings

You are attracted to someone but say that you really don't like the person at all

Undoing

Trying to reverse or "undo" a thought or feeling by performing an action that signifies an opposite feeling than your original thought or feeling

You have feelings of dislike for someone so you buy them a gift