LOL! Whoa, slow down there, man. I am not sure why you think that came out terribly. Let me assure you, sir (or madam, whichever preferred) this does not look terrible! Do not throw the rest of the papers in the bin.
There is a lot to be said about pepakura. It is a tedious often frustrating process, and it takes much, much longer to get a piece finished than it has any right to, but the end result of that frustration and tedious work is a (admittedly angular and digital) great reproduction of a piece of armor. If only you could see some of the monstrosities I had cranked out my first 10 years on the forum, you'd feel pretty dang good about yourself.
I know you said you've studied pepakura for a while now, so please understand I'm not trying to patronize, but I've only seen your one post, and am not sure your true level of experience. (The hand plate looks pretty good to me.) This is the trick with pepakura: Use cardstock, score your paper with a pen or similar pointy thing, and make sure to take your time on the details. Once you finally have the piece done, which can sometimes take quite some time, you'll want to quickly secure its shape by hardening it. There is a lot of discussion around here about how to do that, but I'll walk you through how I did it:
I use fiberglass resin and brush a light coat inside and outside in small sections in whatever way works best to prevent warping (laying it upside down, propping it up on it's side to prevent warping, whatever) and let it dry. This process can take a day or even up to a week depending how hard you work at it. Once the piece is dry and not toxic (Wear a respirator and do this outside......) use the fiberglass resin to moisten fiberglass cloth (again, outside, wear a respirator. And gloves.... Always use gloves!) and place the fiberglass cloth in the piece, covering the entire interior of the part. You will most likely need more that one piece of fiberglass cloth, although with a piece as small as your hand plate there, you MIGHT be able to get away with one bigger piece. Let it dry, then do it again so you have more than one layer of fiberglass resinned into your piece. You will need a Popsicle stick or similar devise to press the fiberglass cloth into place to prevent nasty brain-penetrating stalactite prongs of death from giving you an un scheduled labotomy, and if you get any bubbles you cannot work out, wait for it to dry, then drill a hole in the bubble and fill it with more resin. I'd add at least 3 layers. Up to 7. personal preference. When you're done it'll be as hard as a rock.
After that, bondo that sucker in small increments to round out all the digital angles (Cuz pepakura can't see round surfaces) and sand it smooth until you almost die of old age! Then paint it your desired colors and you're set to go!
TL;DR
Take your time and pay attention to detail. We don't work like microwaves over here; we're like crockpots! It takes a little longer than we'd sometimes like, but he end result is way, WAY nicer.
Good luck! And don't sell yourself short; your hand plate looks good!