right and wrong

How do we define what is good and what is bad?
Seriously if things were to be left to me to decide on all things, there are some "gray" areas in life which i would struggle to say if it was good or bad.
Or do we just FEEL if something is right and wrong by depending on the peace of our heart.
Or do we determine if something is right or wrong by the outcome of it?
Or do we define what is right by the "greater good".

HOw do we actually know if something is right or wrong when we humans are corrupted, selfish people, whom none of us can say we are selfless in all aspects.
There will be situations when we tend to be more concern of ourselves than others.
In safety for example. Would we help a stranger...to the point of sacrifing our own life? Most of us would say NO. why? because there is still future ahead of us....more to live in this world...bla bla bla....
Or if its not safety, maybe its work. Who want to work and not get paid? Yes its sacrificial... but would anyone of us raise our hands and say, yes we would do that....for the long term?
In essence, we are all selfish people, to a certain extent, we do think about ourself, our own safety, our own security.
Often times, we want to get saved so that WE would not get into hell. It is to save OURself from harm. Right to our very nature, all we cared for is our own self, how high we can reach, how far we can go, how great we can be, how nice our life would be.
If all of us are selfish people, how then can we decide what is right and wrong since we only look for opportunities to meet our own desires?

I believe in the Word. And in the Word I stand. May nothing else judge me..not by anyone elses standards but only bythe Bible's standards. Search my heart Oh God, As this relationship I have with you is more than just wanting to be in Heaven with you...but because of the relationship that we have esteblished over the years and I look forward to growing deeper with you.I want to know you more, And I know that it is only by YOur word that things are made right from wrong. And it is only By your word, will you judge your people.
Take my hands and make it yours, That I may touch and heal people.
Take my mouth and make it yours, That I may speak life into people.
Take my feet and make it yours, That I may walk anywhere you ask me to.
Take my eyes and make it yours, That I may see the works you are doing in others.
Take my ears and tune it to you, That I may hear you every second of the day.

Noone will make sense of my life...unless they know you
Hold me close..and let your love surround me..