Originally Posted by Minnesnowta
Also important to know is that indicas and sativas are what they are, so harvesting an indica earlier to achieve a more "heady" effect isn't going to completely counter the fact that its still an indica and is meant to give you a different feeling or effect, and the same goes for sativas. So if you grow an indica and harvest it early expecting to feel all upbeat, energetic, and motivated, you may be somewhat disappointed to find you can't reverse the effects of genetics.
Hopefully that helps you out a little bit. I'm pretty sure that very recently someone posted some much more scientific threads about cannabis flowering/maturity/harvesting and all that stuff. Its broken down into a few different threads based on subject matter, all posted by the same person within a period of about 2 days. And they were posted less than a week ago so you shouldn't have any problem finding them if you want.
Keep at it, stay motivated, stay patient, and stay golden pony boy!