For me, it's just kind of a feeling that this is what and who I am. It has fluctuated over time, however, and I tend to be attracted to people rather than genders. It just so happens that most of the people I've been attracted to have been female and all of my relationships have been with women (except for essentially incidental fooling around with men, 1 of which almost rises/rose to a semi-relationship of a sort). But, labels don't really work for me, and if the stars had aligned right, there are 3 or 4 guys I've known in my life whom I would have had real (i.e., caring and sexual) relationships with.