When one continuously reminds himself that no one can help or harm him, he will even be able to do favors for those that wish him ill will, securely knowing they have no power other then what H'shem gives them.
pg 427
Nefesh Hachaim
Serving H'shem with one's entire soul is the ability to "reach great spiritual heights of love and yearning for H'shem"
Gate Two, Chapter 16 pg 26