A combination of what you do and how you do it is attractive to others (see last post). Similarly, what is attractive about others to you is made up of the same components but is rare and difficult to find if you are a person of discriminating taste.
That is, what a girl does (or says) and how she does (or says) it is attractive to various guys and unattractive to various guys, but the girl who is attractive in both the what and how is exceedingly rare.
If you're having difficulty with women, it's for one of two reasons: you either do not make the effort to show interest, or if you do, she isn't up to your standards. The rest of this blog explains how to show interest. But if you've made the legitimate effort to show interest and you still find it difficult to keep a girlfriend, then the issue is that a woman who is good enough for you has not yet been found.
Here is why it is so difficult: she must share similar interests as you. If you like intellectual discussions and she enjoys drinking and reading the gossip pages, it is unlikely you'll stay together long. Yes, women have different interests than guys and expecting her to be your best friend is not what I'm talking about here. And I'm not talking about someone who is exactly like you. She doesn't have to vote the same way you do or be of the same religion or race. Redundancy is boring. But some common ground is essential. I'm talking a shared background such as being from the same state or having similar family values, or sharing interests such as reading or watching movies. If she likes staying in and you like partying all night long, she's not right for you. If she thinks voting is not important and you do, she's probably not right for you. If it feels like you're talking to a wall, she's not right for you.
But common interests aren't enough. How she expresses those interests are key too. Is she unashamed of stating her desires and interests or tentative? Does she put her interests before you? Is she shy about speaking her mind or does she refuse to try new things? It varies from guy to guy and for you, you might like someone more outgoing or more reserved. You might like someone more dominant or someone more submissive. It varies from guy to guy.
But these two qualities aren't enough to label her your girlfriend or consider her girlfriend material. Sure, on paper, she may be exactly what you are looking for. And you know the life you'd live together would be grand. But if she's not into you, the relationship is one sided. You need to find someone else who returns your interest at least as much, and preferably more.
Take these three factors into consideration, and you'll see why its so difficult to choose a long-term mate. Of course, there is no rule saying you have to be celibate in your search for her or that such judgements can be made in the first interaction.
But it is possible to see in the first interaction whether or not you can and do get along well - whether there is any chemistry. If not, it's not you. It's her. Move on.