How is it not coming out right - placement, image, colors? When I have an idea in my head, I always sketch it out on some scrap paper first, then I prepare all of my materials, cut everything out, color things in, etc. and finally lay it all out before I adhere anything down. I find that by doing it this way, I've got all my ducks in a row and if I'm not satisfied with some element, I can change it out without ruining anything. That being said, I'm wondering if maybe you're being too critical of yourself. Several times I've thought a creation wasn't very good, but when I've come back to it later I've found it to be quite nice, maybe not exactly what I was going for, but still good. Remember - we all our own worst critic!