Okay, I didn't mean to be redundant but I'm sure I got your attention. If you want to be good at something, you need to practice. No matter what it is: writing, quilt-making, singing, piano playing, car repair, hunting, bodybuilding, carpentry, bicycle repair, selling, painting, drag-racing, and the list goes on.
I'm going to pick on the writers out there because it's something I know about, but it also applies to most everything. Whatever you craft it, practice it with excellence. For writers, every single time you lay down your written word, let it be the best you can be. No sloppiness. Even if what you're writing is a simple e-mail that comprises of a whole two sentences, write it with excellence. Others may not recognize it, but you will know.
I'm reminded of a story I once heard about a skilled cabinet-maker. He took so much care on each and every piece of his work, that even the back of the drawers were sanded down to perfection. One day, his apprentice asked, "Why do you put just as much time in the front of the cabinet as you do the back? No one will see it."
"But I'll know," said the cabinet-maker. "And that's all that matters."
Don't do something sloppy that could be performed with more excellence, even if it takes a little longer. Because you'll know.
And that's all that matters.