Sextiles and trines are thought of as harmonious planetary aspects because they create a sense of wellbeing and harmony, opportunity and optimism. You two have no sextiles or trines together, and that can spell real tension in your relationship. Instead of a general sense that things are running smoothly and everything's going to be okay, you might both be waiting for the other shoe to drop -- for the next blowup that you know is just around the corner; for the next disagreement, which you know will happen whenever you try to talk something out.
And while this can make for a very dynamic bond -- hey, it's exciting to have an argument and then make up with true passion -- it can also wear you both out! Having no sense of harmony between you can equal no downtime. It might be all ups and downs, and never any comfortable time in that sweet middle ground. You may even find it hard to agree to disagree; every little thing will seem important, making it hard to keep a sense of perspective. If this relationship is going to last, you're both going to have to develop some thick skin; otherwise, the constant tension could prove too much for either of you to handle.