You two might think you're a good match when it comes to your perspectives on life and the values that you hold dear, but after some time, you probably start to realize that you had it all wrong about each other. You could grow very frustrated with each other when it turns out that what you thought was a lucky winning streak is really a gambling problem; what looked like a healthy sense of self-confidence is really an arrogant streak a mile wide; or, on the other side, what looked like a sensible approach to life is really a resistance to anything new or spontaneous or unorthodox in any way. And boy, are you two mismatched!
You might start to argue about these differences, perhaps subtly, at first. You try to convince your lover of the wisdom of your ways and the folly of theirs. If you're always trying to make the other person see why their way is wrong and yours is better... Well, that doesn't do much for your feeling of solidarity and support as a couple. You're both right, in a sense; it is important to find a lover who matches up with you in all the important things in life, if you want it to last long-term. Otherwise, you two don't stand a chance if all you can do is focus on your differences and the tension that they cause.