Though your lover might have a very demanding career that takes up a lot of their time, interest and attention, that shouldn't hurt your relationship. In fact, their work is important to them, and it becomes very important to you as well. You really identify with their career success, and you want to support them as much as you can in pursuing that success.
The encouragement and willpower that you are able to drum up within yourself is nothing compared to the sense of energy and you-can-do-it confidence that your lover experiences due to your unflagging belief in them. You cheer them on during the rougher times and are there to celebrate all their successes, and what's a success for them is one for both of you. You're your lover's safe harbor, their rock, their cheerleader and their shoulder to lean on when times get tough. It's even possible that you end up working together, whether that means in an office or just as a team at an important function where it's every bit as important to network, meeting and greeting potential clients, investors or other supporters, as it is to deal with those clients, investors and supporters during business hours.