When a person makes the vow to become a nazir he/she is assur from wine and becoming Tamei Mes, amongst other things. When he finishes his Nezirus the possuk says “v’acher yishteh nazir yayin” – “and after the Nazir may drink wine”. Why does it still call him a nazir??
A nazir is somebody who feels he needs to change spiritually, for whatever reason.
He is still called a nazir even after he has bought his Korbonos because even though he can drink wine and become tamei mes he must take his inspiration and purity with him afterwards and hopefully for the rest of his life!!
In the same way when we decide to change our way of life we should make it last a life time, not just for that moment!!