"We do not control grief, it controls us," she said. "You cannot push a person to focus on the future or stop tweeting or throw away the shoes. But we eventually learn to live with it. The grief changes over time. We develop coping skills to fully function again, but it's different from before."
Dr. Katherine Shear, professor of psychiatry in social work at Columbia University, has been a pioneer in studies and treatment of grief.
In 2005, she published the first randomized controlled treatment study for complicated grief, grief that is unresolved and disabling.
"Grief is permanent," she said, but it changes over time.
Grief associated with the loss of a spouse can be "heightened" because of the "every-day-life-ness" and caregiving nature of the relationship.
For most, acute grief is a "very dramatic" experience with unique thoughts, feelings and behaviors, according to Shear.
Intense yearning for the lost spouse is intermixed with sadness. Sometimes it can alternate, even a few weeks after the death, with postive feelings.
"It's a very emotional state that is generally unfamiliar to people," she said. 'One of the typical things that happens is almost a confusion about whether the person is there or not. The idea that they are sitting in the room or a strong expectation that the doorbell will ring and the person will come. Or they will wake up from a dream and he will be there."
Sometimes those who are grieving actually see or hear the other person who died, according to Shear.
"This is perfectly natural and not a cause for alarm," she said. "We can hallucinate during grief."
Another common behavior is to avoid any reminders of the person. "You want to damp down and get control of the emotions in some way," she said.
Anniversaries of a loved one's death can be particularly difficult. "It's a very natural and unavoidable trigger," said Shear. "You can drive down a different street that reminds you of the person, but you cannot escape the day he died."
By the end of the first year, though grief is not over, people generally start to come to terms with the loss of a loved one.
"And then all of a sudden they can be thrown back to feelings they have not had for months and they can be surprised," she said.
That may have been the case with Lisa Nieme as the one-year anniversary of Swayze's death approached. But she told People magazine she is slowly coming to terms with her "overwhelming" loss.
"I know he wanted me to be okay, and I am stronger now," Nieme said. "The fact that I've had some good days definitely gives me hope that I can have more."
As for texting, Shear said it's just another way "to feel closer to that person." Others might embrace a spouse's clothing, or look at a favorite picture or belongings.
"Texting is like talking to people who die," she said. "It may be the most modern way of manifesting a journal. [Lisa Niemi] may know her husband won't get this. But I see this as a kind of compulsion of sorts to get closer to him."
"A person reaches out to look for connections in a range of different ways," said Shear. "It's not odd. It's just like looking at a picture album of a vacation they loved."