Short answer: girls are horny and selfish.
Long answer: Women want to feel beautiful, safe, and women want to be attended to. A man that tosses his girl up occasionally makes her feel beautiful. A man that shows his girl he's fit enough to toss her up, and in tune with his animal instincts makes her feel safe and beautiful. A man that listens to a woman's body and words makes her feel attended to, safe, and beautiful. Don't always be cool, calm, and collected. Show her you're passionate about her. Bite her, lol, smack her ass in public, bite her butt in public. Give into your animalistic impulses sometimes. Show her she makes you a little crazy. Be a little jealous and tell her. Occasionally be a savage.