In his essay, the 47-year-old star detailed the difficulties of everyday life, getting up in the morning and facing the world without the presence of McNamara, reported Entertainment Weekly.
"I can't do it. I can't do it. I want to tune out the world and hide under the covers and never leave my house again and send our daughter, Alice, off to live with her cousins in Chicago, because they won't screw her up the way I know I will. Somebody help me! I can't. I can't. I can't," he wrote.
"I'm moving forward clumsily, stupidly, blindly because of the kind of person Alice is. She's got so much of Michelle in her."
Oswalt further wrote that he tries to remind himself of how his journey to fatherhood began as a way of helping him cope with the challenge of parenting his daughter alone.
"But then I think back to when I became a father. I felt the same terror. And somehow I sort of half breathed in and clumsily took steps forward and I screwed up a lot of stuff - we screwed up a lot of stuff, Michelle and I.
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