Since lust is a sin in the Bible(Matthew 5:28) then HOW does someone KNOW they are attracted to another person?

Big difference between lust and intimacy. When you look at another with only lustful, e.g., want to have with this person just for the physical type feelings, then you're missing out on the true type of intimacy that can be established between two people who really love each other: one that not only encompes physical attraction, but also an extremely special type of intimate bonding that is emotional more than physical, spiritual more than emotional. This requires a great deal of intellectual communication so the attraction is not merely physical in nature, it is much, much deeper. I interpret what the "sin" is as a person who looks at another with the mindset of something like "hmm....I'd really like to !#@$#@ that one to see what it feels like" and has no interest in that person as anything other than a ual object to be used for ual gratification. Think about it.