All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, is His slave and Messenger.
The jurists call the vow that is intended to prevent oneself from doing something, the vow of Lajaaj or anger, and the doer has the choice between fulfilling it or expiating for it, because it counts as an oath.
Hence, you should hasten to repent sincerely to Allah [from your sin], and you may choose between fulfilling your vow or expiating for having broken it.
It suffices you to do either of the two.
You do not have to repeat fulfilling the vow or expiating for breaking the oath if you did not intend with what you said to repeat (the expiation) whenever you break your oath and commit that sin.
Also, for more benefit on the expiation for breaking a vow, please refer to Fatwa 102811.
Allah knows best.