Almighty God can and does give grace to men in answer to their internal aspirations and prayers without the use of any external sign or ceremony. This will always be possible, because God, grace, and the soul are spiritual beings. God is not restricted to the use of material, visible symbols in dealing with men; the sacraments are not necessary in the sense that they could not have been dispensed with. But, if it is known that God has appointed external, visible ceremonies as the means by which certain graces are to be conferred on men, then in order to obtain those graces it will be necessary for men to make use of those Divinely appointed means. If we wish to obtain a certain supernatural end we must use the supernatural means appointed for obtaining that end. This is the reason sacraments are necessary.
#Ref: D.J. KENNEDY