Bhagavad Geeta Precisely.

Whatever has happened, has happened for good.
Whatever is happening, is also for good.
Whatever will happen, shall also be good.
What have you lost, that you cry for?
What did you bring, that you have lost?
What did you create, that was destroyed?
What you have taken, has been from here.
What you gave, has been given here.
What belongs to you today, belonged to someone yesterday,
Shall belong to third person day after.
So why worry unnecessarily?
Change is the Law of Universe.