EcoNoMics... Part 1(selfishness)

Am in the campus library now,
It's the best place in Uni for internet connection and comfort...
Hehe,
anywayz,
just finished my first Economics class...
So far, of all the classes,
I would say I enjoy this class the most so far....
The lecturer is so cool,
He has this amazing Indian accent when he teaches,
He's also quite funny and he makes his class as interesting and interactive as possible...
Being introduced to Economics for the first time(never taken economics as a subject before),
I found out now that it is actually a lot to do with common sense...

Definition for Economics:
"It's a social study on how individuals or institutions and society make optimal choices under conditions of scarcity"

To put it simply,
Economics,
is a study of
HOW PEOPLE MAKE CHOICES....

When the lecturer was giving examples and giving us a first day introduction to subject,
something HIT me into thinking(Yes, I was still paying attention to the lesson)....
The Comic of Calvin and Hobbes(which is one of my favorite comics btw) above speaks a thousand words to what really HIT me during class....

I personally believe everyone is a great Economist...
Why?
Because we are all born as selfish beings on this earth....
We crave for what we want,
we get frustrated, angry and bitter when we cant get it...
Most of the times we have a hidden agenda or motive into doing something....
This in economic terms is called,
Marginal Analysis...
People analyze on what they can obtain if they buy a certain product,
or if they invest in a certain company,
or even if they do something for a friend....
It is all the selfish nature of a human being...
We are taught in class that Never ever let the Cost(sacrifice) be greater than the Benefit(fruit)...

So my question is this...
Is hidden motive fully a bad thing??
Aren't we all driven by something in order to do something??
It's like the law of linear motion, without any force applied to a certain object,
it stays at an unchanged position,
but only with a push, will it move...
Then don't we humans need a "push" too??
To a certain extend selfishness is bad....
But is there a certain level of "selfishness" that moves it into the Grey area??
Hmmmm....

I will only post my response in part 2...
Feel free to help me....
Hehe...
God Bless...