Expectations are a form of positive pressure or motivation.  They are founded in the trust that someone is capable of what you believe he or she can or want him or her to do.  If trust is the ability to believe that someone will be dependable, achieve the goals and complete the tasks that are expected of them; then where trust is expected, expectations need to be reasonable. When expectations are not reasonable, they become pressures that can be difficult to deal with.  In other words:

Overachiever:
This is someone who strives for perfection in every situation and becomes extremely emotional in the face of a win or a defeat.  He is known for overreacting to failure.  An overachiever is never simply happy with his performance and must use others to compare how he did.  He not only feels pressured by others, but also puts an unnecessary amount of pressure on himself.

Slacker:
See the above definition and think of the opposite type of person, because I am too shiftless to write a definition.  Does that seem a little lazy?  Well, a slacker is someone who avoids work or effort at all costs and prefers to avoid active situations.  They tend not to live up to anyone’s expectations to such a degree that people just stop having expectations.

Rebel:
This is someone who purposefully does the exact opposite of what is wanted, needed or expected.  He is never dependable, but the lack of trustworthy acts is deliberate.  The only thing that you can rely on when dealing with someone who is rebellious, is that he will always be unreliable.  Generally, this person has the capabilities to live up to the expectations that are set, but he does not respond well to pressure.