Sex and relationships are supposed to be WIN-WIN.
Casanova got it right. But, you can still "get" sex with selfish intent.
The difference is the repetition with the same partner. Women can sense when you're outcome dependent. They may still have sex with you - one time.
If that's all you want - cool. But, if you want a sexual relationship, you need to make it a win for you and her.
You'll get more pleasure out of it too because sex will sever less as an addiction - desperately and anxiously needing to scratch an itch, and become more like an all you can eat buffet of your favorite foods; accessible anytime, anywhere.