Theory of Good and Correct

I always had this great confusion about how in the world someone know whats good and whats right. Of course everyone can differentiate between good and bad, but how exactly can i know if the good i am doing in also the right thing to do?
A great deal of experience which i have got out of my numerous relations have taught me that we as persons mostly do what is good for us, but hardly anyone of us ever give it a second thought that is it is the right thing.
when i was doing my posting in burns ward in my hospital, i had this lots of cases where i see people suffer daily i knew mosy of them die, but still many times we will find some way to keep them alive even if it is for 2 or 3 days. there is a point when the suffering gets beyond limits and even those (family members or friends) who are with these patients are not bothered about the pain what these fellows are suffering, hearing to all those screams becomes a routine, and there is nothing that could be done to relive that pain, cause the medications that we give is already on the maximum dosages. It used to make me think may be i am following the rules what have been created but is it correct to let those people suffer. I never had an answer.
Some times when it gets really busy in casualty i would just want to let the coming patients go and not bother me some how. When i am too tired i wont be examining then with as much efficiency, may be cause i am pissed off.There was this patient who went against medical advice and i knew he will die if he leaves, and i did nothing to stop him from doing it.
Once i told some one that i love her just to save her from depression but later i got in a lot mess after that. Was it good or correct?
what if i tell someone something that may help this person regain his/her lost confidence not minding is what i'm telling is a lie. Good or correct??
We may do good for ourselves a lot many times when we dont bother that our activities might hurt some one of family and friend.
we may run whole life after career, never knowing who is left behind,and who all we missed in the path to success,everything may be good but was it right?
Its been a really long time i have been haunted by the same question and i have never been able to decide of the things what should i do? the good one or the right one..Most of the times i do things thinking how would a good one or the correct one affect me, i dont want to make any sacrificies if there are any to be made.I dont want to be the one at loss..
And i hope some day i will have answer to do good or correct.