It's quite basic actually: if you meet somebody during a "high" (as in: a party, rave, concert, whatever makes emotions go up, especially if it includes the intake of alcohol or drugs), it creates the utopian expectiation that the "high" is the norm state. If life reverts back to normal, the expectation can't be met, making the relationship feel boring, shallow or even depressing. Thus, it's a sure way ticket for an early end.
So for a relationship to last, it's better if it started (as in, you get to know each other, not neccesarily romantically) during your every day live. Then, even if the romatic parts starts during a "high", it still ahs better chances to last, as you know each other outside of that exceptional situation.