real strong, psychologically strong in mind, he will prefer you being not that "easy"--have your own ideas/career, etc... why he chooses you over other women? there always are many more women beautiful that you, younger than you, and eager to get attentions from him (if he is successful,or attractive...), in this case, i think your mind (intelligence, or characters) is the only way to attract him and keep him for long, you are the challenge to him, right?
only those who is strong outside(pretended), and weak inside (real) person, will prefer woman like a sheep, totally because he knows deep inside (not confident) that he cannot handle you and cannot keep you.