Why do women start crying after they have had great sex with you?

Its similar to why people cry when something really great happens, like if you won a million dollars or held your child for the first time. Its just a release of emotion. Then best things you can do for her is just hold her close and just enjoy the feeling of holding her in your arms, that will comfort her and make her feel close to you. Crying is not a bad thing, so dont worry about it.