In the beginning of your relationship, this person felt they really had a lot to offer you in terms of where you're going in your life. They believed that the two of you are actually on a path together, that you have similar goals, aims and ideals. They offered you all kinds of advice and guidance based on that assumption.
But over time, as they know you better and better, they start to realize that you're actually not on the same path at all. You two might start arguing about what the other is doing, because it feels to you as if they're acting in direct conflict with the needs of the relationship. Actually, they are your needs that are being tested and perhaps not met. If your partner has a high level of insecurity about the stability of the relationship, this aspect only exacerbates that feeling. They could start to see where you need to go, but if it leads away from them, they could deliberately advise you to steer clear of that path -- just to save themselves and their own sense of security! This isn't exactly intentional, and it definitely isn't malicious; but it could happen. Instead of letting this be the case, you must both instead try to pay close attention to what's best for your lover, instead of only considering what you think is best for you.