Needs versus Wants

"We do what we have to do so we can do what we want to do" - ripped from the Chairman's MSN.

I was pondering over this and faced a fundamental problem. I can't decide what to classify under which. Perhaps many things are viewed as wants? Its too sad to consider anything as need and want being really frivolous wishes. Maybe, I lead a life of frivolous wishes.

A simple example.

Need: I need to eat
Want: I want to satisfy my hunger with yummy food

The need sounds so sad and the want sounds more positive and in control.

The default is usually the "want" version coz enjoyment of food is the fundamental to happiness. In this case, you don't have to do what you have to do first, i.e. you don't need to eat and then, pursue yummy food. The need is not a prerequisite of the one. The want is the need with a more positive attitude.

Another example.

Need: I need to study
Want: I want to pass my exams

Then again, people don't really need to study (unless being told/nagged/threatened by their parents). No one ever dies from not studying. The reason why people want to pass their exams is probably due to factors like, since you spent time, since you paid for exams, since the whole world knows you are taking an exam so you jolly well pass it.

Okay, the need leads to the want. Perhaps, the statement above is right.
Conclusion: I need to study in order to pass my exams, and I badly want to pass it.