Q. Does anyone keep all the 613 commandments?
1. The practical answer: many commandments only apply to certain groups (kings, farmers, judges, women, kohanim, etc.) or certain places and times (the land of Israel, the time of the monarchy, etc). Some generally apply only once in a lifetime (marriage, etc.) and hopefully some never (divorce, etc.). Those that affect all of us all the time may be only about 100.
2. The theoretical answer: Rabbi Mendel of Kotz says that if God had expected perfect observance of the commandments He would have given the Torah to the angels. God understands that no human being is perfect – but we are all perfectible and we can constantly improve.