There is so much going on with the average life, many people feel as though their free-time is virtually non-existent anyways. When you throw in self-employment, working at home, kids, or financial distress (and the lack of flexibility to "buy time", such as ordering out instead of cooking from scratch) into the mix, it becomes exponential.
Generally, authors will have most or all of these factors working in their lives. It drags on your psyche, making it harder to focus on details (such as grammar) or to be creative. This means that an author's job just got more difficult.
Don't get me wrong. Most careers have their own version of this. This isn't a whine about how tough it is for an author. It's a reassurance.
Authors (and other creatives) often struggle with confidence in their abilities. The slow nature of sales can compound this. The lack of concrete responses to marketing doesn't help. All-in-all, there is a reason for stereotype of the alcoholic writer.
Trust me on one thing, though. None of that is a reflection on your value or skill as a writer or as a person.
We need to hear that more often. No matter how much we feel as though we are failing, it really isn't much of a metric. The history books are filled with artists and authors who were considered failures right up until their deaths.
So, if you are reading this, you aren't dead - you've still got a chance to make it. Keep writing!