I definitely regret having lost a lot of great learning opportunities because I was fooling around with spoiled, immature, half-formed people. Very few men, at 18, are good enough judges of character to not end up losing badly on this gamble. Most 18-year-old men have certain, umm, influences on their judgment of other people that make them pretty bad at this.
Obviously, some people luck out and meet a soulmate at 18. One of my friends met an amazing woman (also his first girlfriend) in his freshman year and is now happily married. I've seen it happen even in the US, where the average quality of women is low ("hookup culture", Sex and the City) and the odds are bad. I don't think he should count on it, and he definitely should not allow his success or failure with women to affect his concentration and work.