I think there are a couple things you can do. First, I think you can't approach it like "Oh my god, this girl is talking to me! This is amazing! She's amazing. I have needed this!" You have to approach it from a realistic standpoint; she is just a person, not someone who is fulfilling your desire for female attention. She isn't a goal or a prize. She's just someone else, just like I am someone else- she just happens to have different anatomy from you. I think most men can understand what it is like to long for female attention, and it is this longing that i think can create a false impression in your brain: she is attracted to you, and you need her. Maybe she is maybe she isn't, but the point is she isn't the solution to a problem. She isn't the answer to your prayers, and you don't need this particular person anymore than she needs you. So don't go throwing yourself into a situation where you end up making yourself feel like shit because these overblown expectations don't pan out. Now all that may be easier said than done. If you are a young guy, and you have not had a whole lot of experience with interacting with women in an intimate way it might be difficult break those thought patterns because you need to re-progam the way you think about women without knowing any alternatives to the way you are currently thinking about them.

I would say to keep in mind the advice above, but i think a good place to start shaping your future actions would be to look at situations like the one OP was in and learn from them. She and this guy had sex. Obviously he enjoyed it, and wanted to do it again. In this particular case that probably wouldn't have happened regardless of what he did afterward because the sex was bad, and he told her he loved her (it should be evident that this is a no no). But lets say that the sex was enjoyable, and he had not told her he loved her. Everything that he did after that was still fucking cringey, and would be regardless of the quality of the sex. Instead of popping up everywhere unexpectedly, and trying to insinuate himself into her life with the goal of creating something more, he should have been much much more passive. Again, she is just a person, like you, not a goal. If she wants to fuck you again she will. So instead of everything else he did, he might friend her on facebook, and that is pretty much it. Maybe send her a message some time later, but not something that would be overt in its intention to re-engage physically. He did it once. It was just sex. It isn't an excuse to get attached, because again she isn't a prize- she isn't there to fix your loneliness. She fucked you. Now let it be.

Now let's say you still can't get past the sex as a goal thing. In that case you still want to follow all the advice above. Women don't like to feel like they are a target, and they don't want to be made to feel like you are trying to force them into some niche for your own fulfillment. If you are looking to get laid, don't be an asshole, and don't make a fool of yourself. Be calm and collected. Don't rush to fall for someone or to fuck someone. Let it be, hopefully get laid, maybe one day things turn out in such a way that you will have mutual feelings with the girl of your dreams, but mutual means her coming to the same conclusion on her own rather than you forcing yourself into her life in the hopes of something more.