I've thought about this for a while now, and I still think it
isn't fair to label people who are stuck in the mourning stage
'weak personalities'. 
Think... what if the couple was already at the threshold of
marriage with the invitation cards sent out and all that?
Or, what if the couple was very close and intimate... and I'm not
referring solely to physical intimacy - I think emotional intimacy
is even more precious because not everyone can go on a deep level
with someone and to have earned the deep resounding trust of
another soul is indeed very precious... and then, to have that
trust betrayed... it's going to feel like the world has crumbled
under your feet. 
Some people love 'deeper' than others. It's hard to measure since
there's no love gauge per se... but what I mean is, there are those
who love deeply and those who love 'sensibly'. There are people who
enter into marriages because they're in the throes of a deep crush
or infatuation, others who do so because it's a 'marriage of
convenience', ie. he's got a steady job, he can provide me with a
good lifestyle, our families are of similar 'status', etc. but
there are the romantics who marry because they love someone truly,
madly, deeply. The love someone till it aches and they will gladly
yield their very life if necessary, to keep their loved one safe.
And even if their loved one should suffer from a stroke a day after
marriage, they will STILL uphold their marriage vows and not
abandon that person... DEEP love...
In such situations, if the loved one is lost or dumped, the
mourning may take ages... years even. If you've met a soulmate,
only to have that soulmate turn their backs on you, you don't mourn
for just a few days... trust me, you may mourn for YEARS.
Of course, if you're the what I term 'One Size Fits All' type,
meaning, it's easy for you to find a partner, any partner, cause
well, you get along with everyone and you don't really have a set
of difficult criteria, then it's going to be a breeze for you to
enter in and out of relationships. The majority of people I know
fit into this category.
But, if like me, you definitely ain't of the 'One Size Fits All'
category, you're super selective about who you keep as friends, you
find it hard to find a kindred soul who actually understands what
you're talking about, where you're coming from, etc. then, when you
DO find that one special person, it is ONE very very SPECIAL
person. Unique. Irreplaceable.
And should I lose that someone, I will unashamedly mourn my loss
for as long as my heart wants to.
If you have lost a part of your soul, a portion of your heart, a
piece of your mind, and a segment of your future and dreams, you're
not a 'weak personality' if you mourn your loss over a prolonged
period.
Afterall, if it was truly cherished and deeply-loved, you don't
really ever entirely get over it...
