I just wrote about this in my hubs. I think it is important to understand that people have an idea for what their career is going to be, the effort they put in and the time they need for it - when adding a relationship it is important to think about few things - you are adding to their life - not being the core focus. When we have someone become a part of our life, it is to understand that it is unfair to assume we take priority. He or she has had a life far before you and an idea of what type of success they want.
But for the person who is adding you to their life- will need to understand that a relationship has needs - time and effort - it may not be balanced, but there will need to be some provision of time and effort..if that equals to be 0-10% of the time on his/her part - it is an unfair balance and it is clear that the job is important. If it equals to 40-50% that means there is an attempt at balancing both - but perhaps the job is necessary to have a future for the relationship - sometimes its necessary for the relationship to have a job. Just depends on what line of career your are in and where you want your success to be.