Is It Possible To Be Completely Faithful?

There seems to be some discrepancy when it comes down to believing that one can be completely faithful to their significant other. That means, no wondering eyes, wondering minds, flirtatious behaviors, etc. But isn't it natural for a man or woman to be "interested" in more than one person? I mean, isn't it okay to look, but not touch? Or can one classify even an innocent glance as infidelity? Below is a conversation between two friends of mine, The Realist and The Romantic, on this subject matter:

* Conversation Begins *

The Realist:To he honest; all men have shit with them.. White collar, Blue collar, ring around the collar..... The all have one thing in common (penis) all men lust for other women which makes us an easy target. Its in our nature..although we grow out of it, the question is when....these very things makes it hard for great guys... You have to trust in whom ever first and. Then allow God to work on him... I know first hand........ I joke a lot but I'm one of the good guys

The Romantic: Not all men! I am married , have 4 children and have never cheated or thought of another woman during my marriage. If I am not at work, I am home! Trust is something that has been built over time. Cannot generalize that ALL men have issues. My father has been married to the same woman for 51 years, his brother to his wife 65 years, his other brother 55 years and his sister 56 years. Over 200 years of marriage between 4 people. I believe that the type of man or woman you become is because of the people and influences you have around when you are growing up.

The Realist: That's bullshit... 1st off u had me going until I said that u never thought of another woman... If you glanced at one ass ,then u thought about it... If you watched some form of Judith or porno then you thought about it... There are some good men out here and I'm sure you're one, but I have to ask you this... Have you ever masturbated and if so what or who were you thinking about .....cause your mind wanted sex but your hand was closest to you ...

The Romantic: I said I have never thought about another woman while I was married, and No I do not watch porno. I have too much respect for the mother of my children to react too such impulses. Quite honestly I have steak at home, why look for hamburger.........

The Realist: Again you were married for 4 years... What were you doing before then ....hmmm mm

The Romantic: Well, Honestly, I was dating and everything that goes with it, but never cheated on any of them either......

* Conversation Ends *

Based on personal experience, when I was with my daughter's father, there were no other men on the planet. There was absolutely no need to look at, fantasize, or talk to any other male (excluding male members of my family) whatsoever. I was so into him that there would be nights I would just watch him sleep, and other nights I was tempted to count the strands of hair on his head. I love[d] him, and remember what it was like to want to be at his side at all points in time. But when things began to turn sour, the devotion and patience level began to diminish. I started to realize that there was no reciprocity and began to wonder what things would have been like if...

So I ask, what does it take for a person to be completely faithful? What makes a person want to be completely faithful? Is it a lack of self-esteem that makes a person feel like they have to stick around this one person, because the opportunity may never rise again? Is it greed, or possessiveness that makes a person never want to leave? Does it depend on the person that you are giving the love to, that makes you want to stay? Feedback, Please?