Now then, my sons, listen to me; do not turn aside from what I say (Proverbs 5:7).

"Because I told you so" is not typically the most effective response in an argument.  We prefer to be won over with logic, reason, enticement, negotiation, and/or appealing to moral imperatives.  But honestly these forms of persuasion don't always work, particularly when it comes to our sexuality (which is the primary context for the 5th chapter of the Proverbs).  I know this from personal experience.  Logic and reason -- using studies and statistics about potential pregnancies, sexually-transmitted diseases, and long-term relational failures -- don't stand a chance against raging hormones.  Enticement and negotiation -- trying to bargain with privileges and rewards for "good" behavior or penalties for "bad" behavior -- just don't work in the pressure-cooker environment of human sexuality.  Even careful Bible study and appealing to moral imperatives are futile, flippantly disregarded by young lovers in the throes of "true love" and sexual temptation.

So sometimes, like it or not, it really does come down to "because I told you so":  using relational capital, trust, and accountability to make the case for maintaining sexual purity (and other forms of godliness, righteousness, and moral well-being, too).

At the end of the day, after logic, reason, enticement, negotiation, and appealing to moral imperatives have proved fruitless, it comes down to:  "Well, if nothing else, I'd like you to listen because I'm asking you to and telling you what I know best, from a more objective, experienced perspective."  And hopefully, if enough relational capital has been built up through the years (through a dedicated period of deliberate investment), this argument might succeed where all others would fail.  A trusted friend or parent can offer counsel that cuts through all the red tape and offers enough clarity to persuade an individual on the brink of foolishness and failure.

Even in these cases, it's not easy to overcome temptation and selfish desires (especially when it comes to sexuality).  But with a little bit of empathy, encouragement, and accountability, "because I told you so" can be a remarkably effective line of argument.