It's quite simple I feel. The human being is fallen and the 'flesh' so to speak is the generator of all fallen desires, This is why I say that Jesus did not have the same base desires as us because the Bible plainly states that:
"
the sins of the father are passed down upon the son"
Jesus had no earthly father, His Father is God and '
God has no sin'
This is how He overcame the temptations, no earthly man could have done that asides from '
Adam in the garden'
This is why
'Jesus is the second Adam'
What complicates stripping it down is the poverty of the language.
But the process is simple.
Lets remove the words lust and desire from the equation because this is where the argument gets very cloudy.
I believe what Jesus was saying was when a married man intentionally looks at another woman other than his wife with sex as the objective in his mind then he is sinning.
It's not an attraction that is sin
It's the
intentional looking at another woman for this specific purpose.
Without the power of Christ within, a person has no control over their base lust because they are acting in accordance with their nature, which is fallen.
Jesus amended the law to make it impossible to achieve any form of righteousness to an honest heart. This is what he came to do to '
complete the law'
The way of the physical law is closed and it serves now solely to convict and condemn as a '
school master for grace'
If a person is born again and has the higher power working through him by way of regeneration of the mind then he has a choice in front of him..
I know from experience that initial attraction can be a trigger to the base desires of the old man, but at that second you are faced with a decision, If you decide to honor Christ and the other person you will not pursue it and it will go no further and it will not be able to turn into a sexually objective force in your heart, there is no sin here.
Pursuing a woman with a respectful heart and honoring her within your mind is not sinful should you like the look of her if you are not married, it's not the same as wanting to have sex with her. If you get engaged and you start (inevitably) have sexual desires then I personally don't feel that is sin, but Paul does say you should marry if it gets to much.
1 Corinthians 7:36
"If anyone is worried that he might not be acting honorably toward the virgin he is engaged to, and if his passions are too strong[
a] and he feels he ought to marry, he should do as he wants. He is not sinning. They should get married"
But if you should decide to pursue the initial attraction with a woman whom you have no right to 'know' (either because you are married or because you don't have an engagement with her) this is in fact a sin within itself at this point, a sin against what you know to be the right and honorable thing to do.
This force '
emanates from the flesh' exactly as James said.
The more you choose to exercise the mind of Christ and choose Him the easier it gets within your mind, its a matter of training! which as we know is all about exercise .
Wanting to have
sex with someone who is
not your wife is a
sin for a married man.
Simple
It is not an easy world with smut being pumped out of every sewer, but it can and has been done.