i don't know you ...
but i can understand what you've written.
i can understand a tad of the 'extent of the devastation'
the sinking into 'something, back to deep, deep within'
the translation of 'happiest days of life' transformed into 'unimaginable loss'
the 'underestima[tion]' and 'miscalcula[tion]'
and the feeling tt you can't be 'truly happy again.'

and if i know you
i would tell you that it is possible.
it takes caring people to listen.
a lot a lot of times of getting caring people to listen to you.
it takes the one who devastates you to continue being around you
and it takes a lot a lot of going back deep deep within, until you've brought light into it, and then it won't be as deep as before.