Actually, when you say external events that takes place that may
undermine this "forever love", is somewhat subjective. It really
depends on WHAT this external event is, and how much deeply rooted
your relationship was in the first place.
But commonly, it is experienced that going through crisis together,
further strengthens the relationship. Having quarelled a lot as a
couple, does not mean impending doom of a relationship. The more
misunderstandings between the two, the more understanding will be
gained.
Because mistakes always give rise to lessons well learned. Unless
of course, an individual is incapable of learning...