A Psychiatrist by the name of Elisabeth Kübler-Ross said it so beautiful about grieving after a person died, she made schematics of the 5 stages a person goes through when a person dies, or in my case, when your heart gets broken and you're alone again

Stage 1: Denial
you denied what happens, you don't want to see or understand why it happens, you just don't believe that a person is dead or that you are alone again and your heart is broken by the person you love most in the world

Stage 2: Anger
you start to feel mad at everything and everybody, you don't know why it happened, why this person, why now, why, why, why and you start to blame yourself of things you neglected in your own opinion and begin to think that it is your own fault and that you deserved it to be alone again or you feel like you could have helped the person more before he died

Stage 3: Fight
you start to see the being angry isn't helping or making other people clear how you feel so you start to do stupid things to get attention, but everybody does it on their own way, one person just runs a marathon and the other just does everything to just get attention and it can get to dramatic measures that it even can seriously hurt the person but with a broken heart it has no meaning to fight, the only thing you can do is stalk the person you want to be with or treathen everybody that comes close to that person but it is something i personaly wouldn't do

Stage 4: Depression
Now the bad things start to happen, you realize that the person really is gone and that you can't rely on him anymore, the person is gone forever and you get such a mental beating of it that you just start to think in bad things, start to think that it will never go away again and in those moments people start to use drugs, start to drink a lot of alcohol or just sit in the corner alone and just want to fade away, but it isn't an option wether your heart is broken or a person you know died, you need to live with it, but when you are depressed you don't think so clearly about it, because you keep thinking about the past and all the good and beautiful things you did together with the person that is gone or the person that you love and only time can heal the wounds and it hurts, I know

Stage 5: Acceptance
The final stage where you got out of periods of anger and depression, you see that those things happened because it had to, you know that you did all you could to make it as wonderful as possible till the end, with the person you died you can say that gave him a good time when you were with that person and that you had a lot of fun and when you look back at your lover you can say (in my case) that it was a wonderful, beautiful and magical time where you learned how to love a person with all your soul and see the good and bad things of love, but this can sound cocky but all time with you was beautiful till the end, and it had to be this way I think, like you said, it is Destiny

Everybody whose heart is broken or lost or about to lose a person close to them, I hope this little story helps you a little with the time of griefing and I wish you all the very best in life and that your lives only can get better and just get out of the corner in the room and just start to love life again, just accept life as it is, like I did :)