Although you got along wonderfully at first, and felt there was plenty of commonality and good feeling between you, you felt less and less so as time goes on. If you got past the early stages together, you probably started to notice a strange sense of dissatisfaction stemming from the fact that your life paths are somewhat in conflict. What you need to feel comfortable in life, as well as in the relationship, might be the exact opposite of what's good for your partner.
If they must travel a lot for their career, but you need lots of together-time and emotional reassurance to feel stable in the relationship, those two needs are equally valid but in direct conflict. That's the kind of struggle you two encounter with each other. You most likely end up feeling frustrated at the fact that your partner is unaware of your needs. It might even seem like they just don't care about your needs in the face of their own, which could be true, to an extent; we must each look out for ourselves first, after all. But doing so doesn't have to mean that they neglect your needs. If you two want to make this last, you should be aware that it takes compromise on both sides. Your lover has to step outside of what's most comfortable for them in order to accommodate your needs as well.