To Perform or not to Perform

I have on my schedule today to do a Performance Test. But I'm starting to wonder if that's worth the time... So far, I have done 4 PTs:

1: totally half-assed it, it barely counts
2: felt crappy about it, but did ok according to the sample answer
3: felt crappy about it, turned in for grading, got a passing grade
4: did during the simulated written day, felt told in control when the pressure of the timed situation was actually on, totally owned it

So... I'm beginning to think that (a) I do well on these when the pressure is actually on, (b) I do decent even when the pressure isn't totally on.. because in all honesty they're sort of a joke, and (c) does practicing really make someone better at these?

What is everyone else doing? I'm trying to be a sheep, so I need a herd to follow : )