To the threadstarter,
The CRUX of your post, after psychoanalysis, it is just simply the loss of your presumed 'Soulmate', and thus a self reflection to share the depression in your mind...
It is only comprehensible, and many would had suffered the same fate and the same reflection, on what had happened, what could had been done better, etc....but such are harmful as it will only lead you to further depression. as loss is loss and there is NO returning back or turning back time....
The truth is that SOULMATE does NOT exists in reality.
Each Human has a lifespan, and it is a journey of life, filled with up and downs, with others that we meet and part with, opportunities, mistakes, and more.
Your meeting with this lady is probably by chance, and it is the chance that you both SEIZED on, to spend and share that the journey of life together, thru the critical 2Cs - communications daily and compromises - to make that journey fruitful and meaningful....
Now that she is gone, all that left is your perceptions of what could had been WHICH will never be, in your mind, to find another like her, and thus the depression.
In reality, as your life is long, you WILL MEET others, and if you used the same 2Cs formula, you WILL find another supposed 'Soulmate' in your journey of life, and once again find life meaningful to share and live for....if only you will give the other party and yourself a chance, thru trial and errors as NO mortal is perfect, and uplift your life out of depression and give another to know you better, to take a chance with you on her own free will........
I wish you all the best.