Even if you discuss your career goals and ambitions frequently, trying to explain yourselves and where you see yourselves going in the future, you have trouble getting it across to each other. Your lover, especially, just doesn't understand why you want to go where you want to go professionally. The way that they think about life, about their own role in society, about what's the most important work they could do, is just different from how you look at the same things.
It's hard to find common ground. It's likely that you came from two different upbringings, which gave you two completely different perspectives on what's important and what's the definition of success. If this relationship goes far, you have to try hard to figure out a way to explain your point of view to your lover, and vice versa. You want to support and be supported by the one that you love, so this is an important hurdle for you to jump over together.