You might feel familiar or important to each other from the start, and you both have the sense that you've come into each other's lives to help reconcile something from your pasts, or keep you on the same track you've been on for way too long now. In some sense, you're right. You were involved in a past life, and you've come together again in this one to settle those old, unresolved issues.
In this life, you may have set out on a career or schooling path that's no longer interesting to you, but your lover takes it upon themselves to be your taskmaster and to motivate you to stick to your chosen course. But people do change, and that course might not be the right one anymore, even if it once was. It would be a shame for your partner to prevent you from reaching out and grabbing hold of new opportunities, just because they think you ought to stick to the old plan. They try anyway, and they start to feel like they're overly responsible for you. You start to look at them as a real drag -- an unwelcome, restrictive influence in your life. It really might be the best thing for you to simply switch tracks and try something new, but if your lover can't give you the space and flexibility you need to do this, you start to feel as if you two just aren't connecting.