Being invested in your career is a commendable quality, but it's important to maintain that elusive work-life balance. If your nightly routine includes coming home from work to talk about work for another hour, you need to reexamine your conversation skills.
Any supportive partner will be happy to listen to your concerns, or hear updates on that important project you're working on. But by allowing work to dominate your conversations, you're not allowing your mind the reprieve it needs and deserves.
Your girlfriend is not your therapist or your career strategist. She's your lover. Whenever possible, you should be laughing and having mutually entertaining, lighthearted conversation. A good way to a put a foot in the right direction: Start by banning conversations about work at dinner and in bed. Because really, you should have more interesting things to talk about.