When you are in love, how do you know it?

OlderAndWiser u
My girlfriend is Chinese. I know that I love her. Obviously, if I hear myself telling her "Wǒ ài nǐ," or "I love you," then I am reminded that I am in love. But I also find myself being protective of her, nurturing, wanting to do things for her, wanting to keep her safe and secure. I want to hold her close sometimes and I feel better just being close to her. And I know that some guys will want to call me names for showing my feelings in that way, telling me that I shouldn't treat any woman like a queen, but you should also know that she treats me like a king. Before I come to visit her, she makes sure that she has my preferred foods and beverages, she wants to do things because she knows those things will make me happy, and she comes to visit me (we live 80 miles apart) as often as I come to visit her. At each house, we have an identical set of coffee cups:
Mine. . .
Mine. . .
and hers.
and hers.
Aside from hearing "I love you" coming from your lips, how do you know (or what do you do that serves to remind you) that you are in love?
When you are in love, how do you know it?
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