It is not your responsibility to groom your partner into an adult, but it IS your responsibility to motivate them to greatness. Maybe it's a slippery slope, but I'll try to explain.
The idea here is to help them develop themselves, not to poke them with a cattle prod to do what you THINK they should be doing for you. There shouldn't be anything directly self-serving about this at all. This is not a mandate to change a person's goals to yours. The point of it all is to support your partner because a.) they are a direct reflection of you and b.) you genuinely want better for them. If you have your stuff together and they don't, it will eventually put strain on the relationship and minimize chances of a union (if you're thinking about marriage).
As someone's significant other, it's a part of your role to know their potential and know when they aren't making moves to reach it. (moves that satisfy progress, not you personally) Just knowing their potential isn't enough, however. You have to apply that potential to whatever your partner is passionate about. For example, if your partner is constantly complaining about their job and have a vision of where they want to be career-wise, you have to make sure they stay focused to achieve their goals. If they aren't applying for jobs and only complaining, address it. Motivate them to do something about a situation that they don't want to be in. Hold them accountable to their dreams as a good friend and partner. This doesn't mean doing the legwork for their dreams, but it means speaking up when you notice they are dormant or off-task. Suggest ways they can reach their end-goal. Plan with them and show them you are supporting them. For the job example, throw out companies or business ventures that may support their vision.
There shouldn't be a space in a relationship where it's awkward or unwelcomed to be alerted when you're slacking. Welcoming this type of feedback will keep you honest with one another in several areas. No topic should be off limits! Agree on the approach and level of aggression to use when commenting, but keep an open door policy both ways. You know the greatness in your partner better than anybody else. If that means activating and/or reactivating it, it's worth the effort for the end result. Go be great and influence greatness!