| A caveat: your conscience is not yours.
When one refers to one's conscience, one is really talking about all the morality and prohibitions one has received from parents, society, media, etc., and internalized.
Your conscience is part of the meme machine that is your mind; an agglomeration of external influences, ideas and opinions.
It is true that you can only look to yourself as the final arbiter of the morality of your actions; but be aware of whose thoughts you are thinking. Analyze your conscience. Keep what's useful and throw away the rest.
Most of the things you feel guilty about are harmless.
A response to gitm's comments:
My writeup is not intended to be self-contradictory. My admonition to analyze one's own conscience implies the very synthesis process you are advocating. The writeup attempts to address the fact that a large number of people do not do this and, instead, take their conscience at face value.
"Conscience" as it is normally discussed is essentially programming. When people cry out to others to "use your conscience", what they usually mean to say is "adhere to the accepted mores and taboos of our society!", regardless of the "objective" value of those mores and taboos.
I think it is more useful to ask people to use their consciousness; to explore their thoughts and feelings and arrive at a more truthful and beneficial mental state. Your mind is a tool, not a prison. | 
