If you recognize the truth of the Torah, you know that it really is not a choice. You are Hashem’s creation, His slave. You owe Him your existence, and He demands your compliance with His Law.
This is the reason to serve Him ??? ?? ??? ???? ???. You are to serve because that is who you are; you are to have a slave mentality, which means that you are not to have the capacity of thinking about personal gain. There is to be no such thing as personal gain in your world.
If you (like nearly all other people) are not yet at the level where you can completely identify with this ideal, you are encouraged to serve Him ?? ??? ???? ???.