You learn a lot from your relationship with each other, and not just about yourselves, love or the ways in which two people can connect and grow together. You learn all those things too, but your lover, especially, also gets a wonderful and much-needed lesson in pursuing their career. Especially if you are further along in your career than they are, you're able to set a really good example for your lover in terms of networking, self-promotion or even just seizing opportunities as they come up.
Even if that's not the case -- even if you're both already established professionally, or if neither of you has actually started your career or even settled on one yet -- you're still an inspiration in this area of your partner's life. You're right there with them along their professional journey, cheering them on when they meet with successes and lending a shoulder or an ear when they need some comfort and commiseration. In fact, communication is a big strong point between you in terms of taking strides in your careers. You help your lover to brainstorm tactics for advancing themselves, you offer them important advice that helps them to make better decisions in business and you give them a lot of encouragement to get out there and make things happen.