Are you traversing the space and time for the sheer joy of it, or is there a higher purpose for your travels? If it's the latter, well, you can hardly be blamed.
My own work, in both the dreams and in real life, often sends me away from home at long stretches of a time, and there are plenty of men and women in the service who have found and kept love. I would hardly say that distance alone makes you a poor girlfriend. Of course, my own engagement could not handle the strain. If, however, there are other reasons why you would consider breaking up, it may be for the best.