关于如何以图形方式创作的建议

I've always felt that my graphic design skills have lacked, but I do have a desire to improve them. Even though I'm not the worlds worst artist, it's discouraging to see the results from a professional designer, who can do an amazing mockup from a simple spec in just a few hours. I always wonder how they came up with their design and more importantly, how they executed it so quickly. I've always felt that my graphic design skills