It could be hard to get to a point where you really feel like the long-term is a possibility for the two of you, because you just have such different ideas of what's important in a relationship. For your partner, an intellectual match is really important -- but that's not likely what they find here, or at least they don't think yours is a meeting of the minds. Your lover might even create a situation in their mind that doesn't exist in real life.
They convince themselves that you aren't as smart as they'd wish, and there is always something lacking in the way you two communicate. Instead of being calm and accepting about this, they're more likely to get mad about it. They could start baiting you, trying to spur you into an argument, patronizing you or belittling your intellect. That's no way to be treated by someone who's supposed to care about you! But you both feel the tension and the friction when you try to talk things out. Neither of you gets where the other is coming from, and your partner is probably more focused on getting their own side of things explained than on hearing you and really trying to understand you. Needless to say, the relationship suffers as a result. For things to last, you need someone who supports you, who gets you, who allows you to speak your mind and who doesn't make you feel stupid or silly. And that might be hard to find with this person.