I've read a lot of books about grieving these past few month and one thing they all say is that grief is not a straight line. You don't march steadfastly forward, making good progress each day until one day you reach the promised land of restored equilibrium.
No, grieving is more like dancing on the deck of a small boat in a rainstorm. Sometimes you are upright and feeling the sprinkles on your face; other times it's all you can do to keep your footing. Sometimes you are sure the storm is nearly over; other times all you can see is the looming darkness.
The other odd thing about grieving for me is that I don't always identify it as such. Certainly sometimes I can struck by the waves of sheer pain of missing my mother, but other times, I don't actually realize that what I'm feeling is probably grief. I think I'm feeling anxious, or tired, or depressed, or nervous, or worried, or lazy, or foggy, or distracted, or hungry, or lonely. And yes, I am feeling all of those things, but when I stop to consider it, 9 times out of 10, the underlying emotion is grief, wearing a distracting hat.
Another thing that goes along with the many hats of grief is that I'm feeling impatient with myself. I want to be done with this, have it be over, be back to some sense of "normal" again. But dancing on the deck of a boat isn't predictable, even if I want it to be.