You have a hard time meeting this person's needs, though you genuinely want to do so. You try your hardest, putting their needs before your own, but nothing you do is ever quite be enough -- and you feel used and taken advantage of after a while. It isn't that your efforts aren't enough, but more that they're misdirected.
You just don't understand very well where your lover is coming from, so it's hard to figure out how to make them feel good. What each of you wants out of a love affair is likely very different; one of you might want a lighter, more humorous, friendly attachment, while the other wants something serious and emotional. In that type of scenario, neither of you really gets what you want, and you feel irritated as a result. In fact, the small irritations of your day-to-day relationship are what build up over time and cause the most problems. Your tastes differ so much that if you were to move in together, for example, or work on a creative project, you'd have a really hard time settling on anything that you could both be happy with! Though disagreements over your personal aesthetics might not seem hugely important, somehow, the arguments take on a significance of their own, not to mention the fact that it's so hard to get along. Other more harmonious aspects help mitigate the difficult effects of this one.