Yes. It is natural. It is natural to have her on your mind every moment of every day. It is natural to think constantly about what you could have done to change things, or what you should have done. It's natural to wonder how things could have been different.
It's more than natural; it's love.
It's also natural to want to scream out into the night sky. It's natural to cry out for help, but to realize that no one can truly help you but her...
But, as much as the above is true, it's also natural to move on. I know right now it hurts, it hurts like nothing you have ever felt.
Days go by, then weeks, then months, and you may not feel like you're moving anywhere, but you are. I know I worried for the longest time that I would never recover. I really did. Every day I felt no better than I had the day before.
Then, exactly six months later, it happened. It just stopped. The hurt disappeared.
You will move on. It will be hard. It will test every bit of willpower and emotional strength that you posess. But one day, it will happen, and you will be stronger for it.
Good luck with it all.
-Z
"Nothing takes the taste out of peanut butter quite like unrequited love."
-Charlie Brown