As I said before, I think it would be good if you get in the habit of trying to predict the votes that your posts get beforehand and then not post when you think that a post would produce negative karma.
One way to do this might be, whenever you write a post keep it in a textfile and wait a day. The next day you ask yourself whether there anything you can do to improve it. If you feel you can improve it, do it. Then you estimate a confidence interval for the karma you expect your post to get and take a note of it in a spreadsheet. If you think it will be positive post your comment.
If you train that skill I would expect you to raise your karma and learn a generally valuable skill.
If at the end of writing a post you think "I’m not sure where I was going with this anymore." as in http://lesswrong.com/r/discussion/lw/mzx/some_thoughts_on_decentralised_prediction_markets/ , don't publish the post. If you yourself don't see the point in your writing it's unlikely that others will consider it valuable.
and learn a generally valuable skill.
I second this. This is also a very important skill for work and personal emails, and anything having to do with social sites like Facebook.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.