The Facebook post has gotten more than 83,000 likes and 15,000 shares

Comedian and actor Patton Oswalt has penned a heart-breaking letter about his grief three months after his wife, crime writer Michelle McNamara, died in her sleep on April 21.

Oswalt, who has written occasionally about the loss of his wife, posted his in-depth note to Facebook on Monday night.

The post has been liked more than 83,000 times and shared by nearly 15,000 people.

He begins the letter by comparing depression to a schoolyard bully and then explains that depression pales in comparison to grief.

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Patton Oswalt (left) has penned a heart-breaking letter about dealing with grief since the loss of his wife Michelle McNamara (right) three months on

'Grief is Jason Statham holding that 4th grade bully's head in a toilet and then f****** the teacher you've got a crush on in front of the class.

'Grief makes depression cower behind you and apologize for being such a dick,' Oswalt says in the post.

He continues saying 102 days - the amount of time since McNamara died - is enough time to accomplish miracles.

But Oswalt, who married McNamara in 2005, says 102 days isn't long enough to heal the gaping loss of his wife.

'102 days at the mercy of grief and loss feels like 102 years and you have shit to show for it.

'You will not be physically healthier. You will not feel "wiser." You will not have "closure."

'You will not have "perspective" or "resilience" or "a new sense of self."

He continues saying 102 days - the amount of time since McNamara died - is enough time to accomplish miracles but isn't enough time for him to move beyond his grief. Oswalt, who married McNamara in 2005, says '102 days at the mercy of grief and loss feels like 102 years'

Oswalt's note (pictured), which was posted to Facebook on Monday night, has been liked more than 83,000 times and shared by nearly 15,000 people

'You WILL have solid knowledge of fear, exhaustion and a new appreciation for the randomness and horror of the universe.

'And you'll also realize that 102 days is nothing but a warm-up for things to come,' he writes.

Then, the tone of the post shifts away from the darkness of losing his wife to thankfulness for the people who have supported and loved him during the last three months.

'You will have been shown new levels of humanity and grace and intelligence by your family and friends.

Oswalt also thanked those who have offered their support during this time and have reached out to him

'They will show up for you, physically and emotionally, in ways which make you take careful note, and say to yourself, "Make sure to try to do that for someone else someday".'

'Complete strangers will send you genuinely touching messages on Facebook and Twitter, or will somehow figure out your address to send you letters which you'll keep and re-read 'cause you can't believe how helpful they are.

'And, if you're a parent? You'll wish you were your kid's age, because the way they embrace despair and joy are at a purer level that you're going to have to reconnect with, to reach backwards through years of calcified cynicism and ironic detachment,' he writes.

Next he talks about his seven-year-old daughter with McNamara, Alice.

He says before McNamara was 'yanked off the planet' she put all of her goodness into Alice.

Oswalt says immediately following McNamara's death he was 'face-down and frozen for weeks'.

After three months he says he's finally started to 'crawl', which is an improvement.

Oswalt says immediately following McNamara's death he was 'face-down and frozen for weeks'. After three months he says he's finally started to 'crawl', which is an improvement. He hopes after another 102 days he might be 'walking'

He hopes after another 102 days he might be 'walking'.

Oswalt also says he's finishing a book about the 'The Golden State Killer', as McNamara called it, which delves into a murder mystery about a California serial killer.

All of his energy has gone toward finishing the book, he says.

Finally, he tells his fans soon he'll start telling jokes again, writing and acting - not because 'what Michelle would have wanted me to do', which he says he has no way of knowing.

'I'll start being funny again soon. What other choice do I have?

'Reality is in a death spiral and we seem to be living in a cackling, looming nightmare-swamp.

'We're all being dragged into a shadow-realm of doom by hateful lunatics who are determined to send our planet careening into oblivion.

He finishes the letter by saying: 'Hey, there's that smile I was missing!'

McNamara died in her sleep at her home in Los Angeles on April 21, according to Oswalt's publicist. McNamara was 46 years old.

McNamara graduated from the University of Notre Dame and received a master's degree in creative writing from the University of Minnesota.