Gave back all my profit plus more from yesterday today. I was expecting that Bush's speech on a stimulus package would cause a mini rally to squeeze the shorts. So I kept entering trades on the Buy signals. As you can see from the graph, it didn't happen. Stupid me. The parameter is definitely too loose at the moment on the Buy signal. I have adjusted it now and it seems to be a bit better (fewer false positives).
I also shouldn't read too much into comments from Bill Cara's blog. Both times I went against my own judgement because of reading too much of other people's comments led to big losses. Lesson is to never have any expectation of the market. See what the price is doing and interpret it based on that, and that alone. End of story.
In total, I think I'm down about a \$500 from my YM day trading for the past couple of weeks. If there's any consolation, I think my system is improving from these failures.