Note, I am not talking about complaining about/to God.
I am talking about complaining in general.
For example - I really hate it when my kids leave their clothes on the floor. They have a shower and leave their towels on the floor. They leave their dishes on the table. They leave their crumbs all over the counter when they make their sandwiches for lunch. They never do their practicing, etc, etc, etc. And today, it is raining, my flowers will never grow, it is so miserable and I have to stay indoors all day and if I do go out it will be so unpleasant as I will get wet and the kids will track water in throughout the house, and if the dog goes out when he comes back he will stink, and the newspaper will be wet and it will be hard to read, not to mention that the newspaper is so awfully slanted these days…etc, etc…etc.
Note, I am not complaining here about my kids behavior - I don’t want you to suggest ways to correct their behavior, I am talking about constant criticism with no attempt to correct their action. Just the deluge of complaints. Is this a sin? If so - what commandment is it a sin against. How should a penitent go about correcting this sin. It seems to me - that at its nub it is a lack of gratitude.