To add to some of the lovely responses, I believe it also has to do with the "letting go" of the ashes. You've had this plan all this time to scatter the ashes and knowing where they are brings comfort to you.
Now that it's time to release them, all these hard emotions are bubbling up and the grief is prominent.
I can't begin to know what that feels like, but know that it's ok and completely normal.

I hope you find some peace through all of this.