I use characters that I make up (and possibly are from my writing) that would be similar to me (would be the version of me that would exist in the particular fantasy's universe), but be better than me in certain ways. In both looks and personality. I like fantasizing in a universe where I'm a capable of seducing someone. Or frankly, in a universe where I'm psychologically able to have sex. I mean, these are going to be my only sexual experiences, so I might as well try to make them good if I can.