He behaves and thinks like a 45 year already, taking responsibilities, worrying about reality. All the time, It is said that "Wo jawani hi nahi jis ki koi Kahaani nahi"
And here is a 25 year old who has neither living his Jawani (youth) or getting to write his kahaani (story)
Why Abhishek needs Meera because she makes him this 25 year old carefree youth, even if only when he is with her. And why she needs him is because she needs that unconditional acceptance which likes her for what she is.
M