I have been asking a few married brother about the meaning of this Hadeeth, what exactly does it mean?
The family is the smallest unit of society, but this is actually the most important unit in the Muslim community.
In a family, a child will begin to learn about Islam and learn to be a dutiful child to the parents. In a family, a woman will learn to be a sholihah (pious) wife and a good mother to her children. In a family, a man will learn to be a husband and father who instilled values of Islam to his wife and children, and lead them in the way of Allah. There is a big responsibility in building a Muslim family.
Are you able to bear the responsibility to lead this smallest unit in Muslim society to walk on the way of Allah?. If you are able, then get married. And this means you have reached the half-way to be a saleh (pious) Muslim. And you only have to travel half again by becoming a husband (and father) who lead your family to walk on the way of Allah.
But remember, if you just get married, but never tried to become a leader in the family who guide your family to walk on the way of Allah, then you reach only halfway, and not finish you journey. Or in another word, you get only half of the deen, not full deen.
This is why, after said "When a man marries he has fulfilled half of the ‘deen", Rasulullah Sallallaahu Alaihi Wa Sallam continued with "so let him fear Allah regarding the remaining half". Half is not enough, we should try to get full.
We cannot focus only to "half of the deen", but we must notice the whole words of this hadith.