There is a struggle between you involving the work that you do and the way that your lover feels about it. Maybe your career takes a lot of your time and attention, which you might otherwise spend on the relationship -- which could hurt your partner's feelings. A workaholic plus an oversensitive homebody doesn't make the world's greatest couple, and this is just the type of emotional struggle you're involved in together.
You start to notice a tension that springs up every time that button is pushed -- you talk about your work or mention needing to go out of town on a business trip, say, and your lover just clams up, unreasonably hurt by this news. Unfortunately, if you want things to work, much of the adjustment has to be on your lover's part; they have to grow accustomed to the very things that hurt their feelings. Posing an ultimatum -- 'It's me or your career!' -- is unfair to you, and might not have the effect they hope for. A little insecurity might just be a necessary byproduct of the relationship, for them. If you're able to talk about these things together and keep checking in with each other on your feelings about everything, you actually come through the experience stronger, especially if your lover is able to learn to rely more on themselves for emotional sustenance than on you.