Don't you DARE cut all that beautiful hair off! :x
Sometimes change is good. I just wouldn't go as extreme. That's a HUGE change. Maybe you can take alittle length off to see how you like it. And if you still feel the urge to cut, then go for it.
It's only hair, right? You can always grow it back. But I would just try a less than extreme cut first before diving right into it. Like you said, you don't want to regret going off of an impulse.