You just had amazing sex with someone you could see spending your life with — a really, really good woman, someone who makes you want to stick around.
Now counter-argument three is that she might tell you she doesn't love you back. Usually the woman says "I love you" first, no? Imagine this nightmare scenario. So you keep your mouth shut so you can win a few man points? Men who labor in unrequited love suffer from back problems because their heads are constantly slumped in shame.