Pacing Yourself

I'm not going to say that I'm doing too much, but I've been considering it.  It's taking me a lot longer than I expected to finish the books I've been reading.  Although technically I would be finishing three books at once, I'm in different places in all of them and they're all different lengths and I read them at random amounts (one I hardly read at all).  But it has been longer than I thought it would take.  I'm not trying to race through anything, but I have to make sure I don't lose interest either.  It's very difficult to pace yourself enough to make sure you stay interested and keep moving forward.