You may think you're simply asserting yourself in the only way that comes naturally to you, but when you're in a discussion or an argument, your partner is likely to think that you're being loud, obnoxious, or even purposely standing in the way of their development. Especially if you become intimately involved on a long-term basis, there will be a damaging interaction that seethes between you as you behave in the ways you know to behave, and your partner becomes more and more resentful as a result. This resentment may or may not result from a past-life experience in which you prevented their personal growth, but either way, whether consciously or unconsciously, they will feel as if you're blocking them from moving forward along their rightful path in life.
And maybe you are, albeit unknowingly. The way that you assert yourself and pursue your goals will somehow block their personal growth. In disagreements as well as in regular conversation, you have a way of making your needs and your views known that isn't inherently negative, but it won't have a positive effect on your partner. If there aren't enough positive aspects between you to hold you together long-term, you may find that this aspect becomes a deal-breaker.