You take opposing sides on achieving any goal or moving forward into the future, and this creates tension, to say the least. Your partner is the dreamer -- the carefree one whose less-than-serious attitude makes you cringe. But your overly serious, even pessimistic outlook has a dampening effect on your partner's creative spirits, like water dousing a candle.
Part of the problem is that you represent things to each other that each of you lacks: You lack this person's optimistic outlook and their ability to seize opportunities, and they lack your focus and dedication to hard work. If you can figure out how to blend your individual strengths, then you can really get somewhere as a team -- but that means respecting each other's methods, which might just be too hard. You're a lot more likely to get into power struggles where you're each fighting for dominance, trying to prove that your own way of doing things is the right one. Why not try to learn from each other? Instead of your partner looking at you as being limited and overly focused on responsibility, they could see those qualities as strengths -- focus and dedication are essential to meeting any goal, after all. And what looks to you like carelessness on their part is actually an unquenchable spirit, an optimistic streak a mile wide. Change the way you look at each other, and you stand a greater chance of blending your strengths.