Something happened in your lover's past life, or lives, that made them feel insecure. Thus, in this life, they work hard to make sure that the same experience won't happen again -- that they have everything they need in order to function from a secure base. That's true of everyone, really; everyone has been through a trying experience that exposed their vulnerability and made them want to ensure it would never happen again.
Perhaps realizing most people have insecurities and vulnerability in common will help you to deal gracefully with the relationship dynamic that will result from your present-life connection with your partner; because otherwise, it could be a difficult experience. Over time, if your relationship progresses, you'll begin to realize that what they need in order to feel secure in the relationship is quite different from what you need in order to progress on a personal basis. They will try to discourage you from following your personal muse, and this will frustrate you. You want certain things for yourself, after all; you have goals, desires and opinions, and you'll begin to see that these things -- in essence, your individuality itself -- threaten your partner. You might even start to look at them as a bit of a stick-in-the-mud over time, fixed in their anxieties while you're trying to push forward and become the person you already are, the one you know you can be. Your partner's attempts to control you, criticize you or hold you back in some way won't fall lightly on your shoulders, but communication about your feelings and fears as well as compromise will help lighten the burden.