I haven’t finished drinking the hot bath!
Made me laugh. It’s been years since I heard that one.
Whatever it may be, use of the passive voice is not a grammatical error. At the very worst, overuse of the passive is poor or inappropriate style, and often it is not even that. Use of the passive often is appropriate. There is a reason it exists in the language. If your teachers said you should never use it, they were idiots.
However, if, as you seem to imply, you use the passive very heavily in your everyday talk, people must think you very dull and/or pompous. Perhaps that is not what you really meant, though.)
I am over fond of (and some might say addicted to) the parenthetical aside.
I have to make a positive effort to go back and remove them. I think it’s a leftover from my effort to use less commas.
I also do the declarative with a question mark, but only informally, online and frankly, mostly on Twitter. It gets a certain way of thinking across in fewer characters.
(I really, really need to use fewer parentheticals, though. Really.)
Me first – because I just learned it myself, and right here. 
“Fewer” commas, not “less”.
Use “less” for something that can’t be counted; “fewer” for things that are countable.
I have less space in my new office.
There are fewer parking spaces at my new office.
Did I get it right?
Well, it depends. Do you want the officious schoolmarm answer or the real linguistics fact-based answer?
Either, or both. 
Well, the schoolmarm says you are correct. Less is for mass nouns and fewer is for count.
The reality is, though, that no one really cared until one writer in the 1700s made a comment that he, himself, found such a distinction rather pleasing. And since no one ever went broke gambling on humanity’s insecurities, many people made bank writing books castigating people for breaking a rule that until 1770 hadn’t even existed. Some people have taken this new rule to heart and many have not. Obviously, style guides take preference and a writer is free to write as she pleases. Personally, I like using less with count nouns and I like the feeling of connectedness it gives me with english when I think about King Alfred writing “Swa mid læs worda swa mid ma” in 880 AD and me continuing the construction in my own little way now in 2013.
Comparing grammar usage today to grammar usage in the past — especially that of 1,200 years ago, or to Chaucer or to that overrated hack Shakespeare who wasn’t even Shakespeare — isn’t legit. It’s silly.
Mistakes aren’t mistakes because the same mistakes were made hundreds of years ago in some farcical golden age of English when all was correct?
'Struth!
Using less with count nouns isn’t fine because they did it in the past. Using less with count nouns is fine because it happens all over the place in current english by everyone, regardless of education level and writing ability. When a ‘rule’ is so badly followed, one really should start to question its validity as a rule rather than a stylistic preference.
But one could say the same about any rule of grammar. Structure and meaning would fall apart and all would be chaos.
The youse dont needs right grammer cos yous no what i mean where wood u drawe theline
You say grammar but apparently you mean orthography.
And you can’t say the same, actually, because my argument is not, ‘everything is correct’, it is that the english language is a group effort and if we are to divine what is correct and what is not, we must take into account everybody’s usage.
"Prescriptivists claim that there are certain rules which have authority over us even if they are not respected as correctness conditions in the ordinary usage of anybody. You can tell them, “All writers of English sometimes use pronouns that have genitive noun phrase determiners as antecedents; Shakespeare did; Churchill did; Queen Elizabeth does; you did in your last book, a dozen times” [. . .]; and they just say, “Well then, I must try even harder, because regardless of what anyone says or writes, the prohibition against genitive antecedents is valid and ought to be respected by all of us.” To prescriptivists of this sort, there is just nothing you can say, because they do not acknowledge any circumstances under which they might conceivably find that they are wrong about the language. If they believe infinitives shouldn’t be split, it won’t matter if you can show that every user of English on the planet has used split infinitives, they’ll still say that nonetheless it’s just wrong. That’s the opposite insanity to “anything that occurs is correct”: it says “nothing that occurs is relevant”. Both positions are completely nuts. But there is a rather more subtle position in the middle that isn’t. "
Edit: A correctness condition, by the way, is something in a dialect or register that allows or disallows a construction or expression. If your dialect allows for negative concord, then the correctness condition allows you to use double negatives. But there is no correctness condition for negative concord in, say, Standard English of the sort you might use in a classroom presentation, so there you would be incorrect to use a double negative.
Well, I include grammar.
At heart I’m a prescriptivist (my U.K. Firefox with a Canadian dictionary add-on underlines prescriptivist with a red, squiggly line), but I know I’m on the losing side.
Another loss for me: I should have deleted prescriptivist and used another word. The red squiggle tells me so. But I won’t stop flailing against ongoing!
Thanks for the Pullum link (who, it must be said, sticks with the archaic Geoff).
Not sure it’s a grammar mistake per se, but I often repeat words, particularly uncommon ones. It’s the sort of thing that would induce a teacher to write “Thesaurus!” when grading a paper.
Long, tangled and convoluted sentences are my hallmark because, since my mind is one which perceives a number of possibilities in each situation, and I don’t want to go off topic, which I often do, I try to fit all the possibilities and exceptions into the same sentence or paragraph.
That’s my excuse and I’m sticking to it.