Hey, don't sweat it! Play to your strengths. Many people here write short, almost non-reviews, but it's more about letting people hear/be introduced to the music you like than writing novels. I personally run off at the mouth constantly in my journal, but then, I'm an aspiring writer, at least in my mind, so that suits me. Doesn't suit everyone (ask starrynight).
Just do whatever feels comfortable, and don't feel pressured or pushed to produce content you're not happy with. Don't make it a chore: it's meant to be a fun pastime (what? Deadline? What deadline? Yes, yes I'll be there in a minute, I'm just taking a break!)
not an endurance test.
You'll do fine.
Best of luck
TH (heading back to work...)