I think some people really do have a knack for it. Some people can conceptualize what things are going to look like before they happen and they can plan how or what they are going to stitch next and just keep on going. I can't do that and have to stop constantly and figure out where I'm going next and which way I need to swing my needle etc.
Practice is important and can produce a great product, but some people are just natural artists and it seems effortless. The rest of us just plug away.
Watson