A. First of all, nowadays in the Jewish exile (even in Israel) there are many Mitzvos which we can not fulfill, especially those pertaining to the Temple and many of the laws of Purity. Once we already have a set lifestyle, it may be difficult to accommodate all of the restrictions and observances. But to live a full Jewish life is to develop a Jewish lifestyle and lifecycle that incorporates and includes all the different elements and aspects of the Mitzvos. It can almost become natural, part of your way of life. Is it a perfect observance? Of course not. But living Jewishly allows for close enough, if we so desire. By the way, if you tally it all up there are even more than 613, but these are the “listed Mitzvot” , the headers or central aspects of all the Mitzvos.