Most importantly, they did not understand this passage to have anything to do with Americanized dating.
While we view the heart as the seat of our emotions and our will, Israel understood the heart to be the center of the whole person—not just the source of emotions and will but also of wisdom and perspective.
Most books on dating treat the idea of guarding your heart as if it merely involves protecting yourself from too much intimacy with someone of the opposite sex. It’s a call to protect your character in all that you do.
In essence, the heart referred to who you are as a person.
Solomon rightly realized that what you do flows from who you are.
Suddenly the issues of sex and boundaries start to arise, and teens find themselves having to choose sides on "hot button" topics like homosexuality and abortion.
There is a lot of growing to do in all aspects of relationships, and having Biblical and Christian guidance is essential.
It begins with prayer to God (as Paul lays out in Philippians 4:6-7) and overflows into communication with the other person.
In other words, the key to guarding your heart is to talk to God about the relationship before you talk to the other person about the relationship. First, hearts become unguarded when you move too fast in the relationship–becoming too vulnerable too quickly.
That’s why he instructs Israel to guard the heart (who you are) because the wellspring of life (what you do) flows from it.
Therefore, it is essential for you to guard your heart in dating because what you do in a dating relationship flows from who you are in a dating relationship.
This is also why Christian teens need to work at keeping their friendships strong.
Think of the traits that are important in any relationship like honesty and trust, and they apply to your friends.
When you read most Christian dating books, one of the key pieces of counsel they provide is to “guard your heart.” They establish that guarding your heart is an essential component of correctly pursuing any dating relationship.