It happened slowly or suddenly. No matter which, you were not prepared for it. It was a child, or a spouse, or a close friend. It may have been death, divorce (which can just as devastating)  or some other item on the shelf of tragic events that befall us. In each instance, a journey began for the one(s) left behind that no one else can walk.
Others that have walked can look in the window and cry with you and give you hope, but the stark unvarnished fact remains that no human can walk with you. Sleep will come. Fitfully at first, and your pillow will be wet with unwelcome tears that will, in time, become your friends.
The days will move along with a deep loneliness. Some on the journey will wish for death. If your path takes you that direction, it is not abnormal, but neither is it a legitimate exit.  Physical symptoms of your troubled heart will sometimes make themselves at home in your body. Sometimes it will be panic, sometimes a phobia. You might sometimes see the one who can no longer be seen. Like a phantom, a ghost, but very real, and yet unreal.
Time will become your enemy, but, like your tears, will eventually make friends with you. The unwelcome reality is that the pain will remain with you until you die and push someone else onto the road called grief.
You will live with it, make peace with it and learn great lessons from it.  It will become the ghost that suddenly appears, unlocks the chambers of your soul, and lets all that you have so carefully locked away spill out once again. You will however, go on living with purpose, focus,  and even joy. You will look in the window as others begin to walk and give them hope, and cry with them. You will find others who have walked the gamut and have an understanding that comes with no other process, and your heart will find friends who will become one with you in understanding and heart because they themselves have made the lonely journey.
I know of one such man. He was a man of sorrows and acquainted with grief. He was despised and rejected. He walked! And he can show up unexpectedly if you are trying to find the path. His name is Jesus, and he is the friend of sinners, and he's been there. He's my friend! My friend Jesus. Is he yours? Would you like him to be? The man of sorrows died for you and wants you to be with him forever. He paid for your sins, and, after all, sin is what took away that which was so precious to start with. If there was no such thing as sin, there would be no such thing as death. (or anything else that troubles us!) Well, on we go and hold each other up in the storm, and someday, if we know HIM, we'll all be together again! - YES!!!!!