When you two first got together, you thought you really had a lot to offer your partner in terms of where they were going in their life. You believed that the two of you were actually on a path together, that you had similar goals, aims and ideals. You offered them all kinds of advice and guidance based on that assumption.
But over time, as you got to know your lover better, you realized that you two actually weren't on the same path at all. You two probably argue about what the other is doing, now, because it feels to you as if they're acting in direct conflict with the needs of the relationship. But really, it's your needs that are being tested and perhaps not met. If you have a high level of insecurity about the stability of this relationship, this aspect only exacerbates that feeling. You could start to see where your partner needs to go, but if it seems like that direction is away from you, you could deliberately advise them to steer clear of that path -- just to save yourself and your 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.