Excerpt from my latest Sasstrology article (please leave comments on the Sasstrology site):
"The Sun represents your ego and life’s purpose. They are expressed in certain ways (via your Sun sign) and through certain areas of your life (via the house your Sun is in). When your Sun progresses into a new sign or house, there will be a dramatic shift in how you express yourself. This can have a huge impact on your love life, because the essence of who you are is evolving. You can’t ignore the Sun sign you were born with; that influence will remain. But as your Sun progresses, its natal potential develops."