You might not be sharpening your chisels as often as they need, too. In my experience, cross-cutting pine (or spruce) blunts them surprisingly fast. Make sure they're really sharp (see various archived discussions on being able to dry-shave, slice paper, etc!), and be prepared to sharpen them often as you work - say every ten minutes or so. You'll only need to touch them up a bit, usually, but it will make all the difference
E.