Troubling thoughts

Just woke up in the middle of the night after a troubling dream...
I don't know what to make of it.
The troubling thoughts came back to haunt me.
Finally having a better sleep since sick, now I am awake.
Watched a podcast today talking about losing someone you care and love.
They said it's nature to be sad throughout the process.
It shows you have feeling for that someone.
All this time, I still do.
I can't show it because that someone doesn't feel the same way.
I still can't comprehend the fact that I lost her.
What should I do?
Letting go is not easy and I don't want to.
How can people let go of someone who mean the world to you?
I don't know how others do that...