Expression is not as important in interface design as in—for example—graphic design or fine art. Still, many interface designers have a personal style.
You might wonder where your personal style will come from. Especially because you’ll get better by studying other designers.
But you don’t take everything from every designer. As you pull apart more and more design you start to notice preferences. “I like that thick divider”. You might not know why you like the thick divider. It probably isn’t important. Why do you like classical music when your friend likes rap? It isn’t important.
You’ll also notice things you don’t like. Maybe coloured drop shadows turn you off.
As you notice these you’ll make two piles, of the things you do and don’t like. Your personal style comes from the pile of things you like.
Sometimes you will need to design something that you don’t like. That’s fine. A good lawyer can argue on behalf of a murderer.
You should practice what you like. When you design with that style, it should be the best you’re capable of.
But you need to practice what you don’t like, too.