Occasionally one runs across people who worry about developing a personal style, or who talk about their personal style, or who think it is important that a photographer have a personal style. Adam Marelli has a pretty insightful essay here.
Style shouldn't be about you. It should serve the picture, or the portfolio, or the show. The style should support and clarify the idea, the meaning. And by the by, there should be an idea, or some meaning, of some sort.
If you do develop a personal style, it's because the work you do tends to cover some of the same ground, in some sense, over and over. It's because the meanings overlap, and therefore the styles which support those meanings overlap, and therefore the work tends to look similar along certain stylistic lines.
If you're just doing the same thing over and over because it's your thing, you're not an artist with a distinctive personal style at all. You're a one trick pony, and that is a different thing entirely.