After spending some time together, you've both started to realize that your energies are mismatched. There just isn't much intersection in the basic ways that you meet life; you're more careful, conservative and pessimistic than your partner (though you think you're being realistic!), while they're more impulsive and into taking risks. They often adopt a devil-may-care, rebellious attitude that makes you feel uncomfortable.
Because you're so different in your approaches to almost anything that comes up, you find that when you're together, upsets and obstacles come up with regularity. You make plans for the weekend, say, but then traffic slows your lover down, they take a detour and get lost, and then your plans go down the proverbial tubes! This kind of thing happens again and again until you can recognize that your ill-matched energies are actually creating obstacles. Before you're able to make that realization, you both just get annoyed by the slow progress you make as a couple. Issues crop up -- you accidentally offend each other, for example, or challenge each other's sense of duty -- and you respond with irritation, blaming each other even for factors beyond either of your control. Unless you can face the fact that this frustrating energy is actually a product of the two of you together, it'll keep causing you trouble. Compromise helps a lot, as does resisting the urge to point the finger at each other.