Re the Godowsky suggestion, some people interpret this simply as permission to alternate wrist positions in long, tiring octave passages in order to rest certain muscles. That's what I've read in interviews of some of the greats, anyway. Xvimbi, I thought yours was a fantastic explanation of orientation and healthy playing. I have very small hands and play tons of octaves at times, so I wanted to say hi! to the original poster... and echo the thought that pain is BAD. I'm curious about the observation, "my octave technique is not perfect." There is clearly something you're trying to achieve through your long octave exercise that hasn't happened yet, and I wondered whether it could be accomplished without playing quite so many octaves every day. This is only general advice, because I don't really know how it's going for you, but perhaps there is something very specific you're aiming for: more even touch, more accuracy in certain keys, speed. Anyway, I just wondered whether you could spend less time on the exercise but pay even more attention than usual to how it sounds and FEELS, and really concentrate on, as Xvimbi said, allowing your hands to be very natural (small) as much as possible-- only opening for the moment of playing. When we are small, it's tempting to assume a "claw" position for larger intervals and hold that position. This is a bad habit formed for a really good reason: we're trying to lessen the chance of hitting wrong notes, and it seems logical to just pre-form the interval. It seems like it should work, but it doesn't. A couple of big things go wrong: 1. we add a truly dangerous amount of tension to our playing, and 2. we lose-- or fail to develop-- the natural sense of the keyboard that allows us to find the right notes without even trying. When we're stiff, we don't experience the spacings in the same way, for some reason, so not only are we endangering ourselves, but we're also hitting wrong notes. All very frustrating.
I'm afraid this is getting long! sorry, and I'm going out on a limb here, but there's something else that comes up for pianists with small hands. Maybe not for you. Many small-handers are resentful or regretful about their size, and feel very determined to "catch up" to performers with bigger hands. Forgive my comments if this doesn't apply to you... but we might spend a lot of time-- years! trying to make up for our perceived shortcomings (no pun), and if it's uncomfortable, the tendency is to ignore the body and push through the pain toward some larger goal. To anyone who is experiencing this, I respectfully suggest taking a fresh inventory of the advantages of your personal shape and size of hand. Maybe they're small but SPEEDY, maybe they can do intricate passages in which the hands are all mixed up together, whatever. Not to look for ways of feeling superior to someone of a different shape! there is no ideal! but rather to find our own unique assets and really use them in a healthy way to make beautiful music.
Very best wishes, and take care of your hands! They are special!