I can't believe health has nectar...
I completely missed that fact, somehow, and now I'm a bit disappointed at my idiocy. I wouldn't say I struggled with it, but I certainly wasted a lot of time, and ignored nectar until it was quite late (I was already exploring the clock tower and didn't even read the nectar 4 book). I kept Wondering why the developers didn't add a nectar soul element...
Read everything, people, everything.