If one is hurt by his enemy, in no way should he view him as having any strength. He should know that his enemy was sent by H'shem to cleanse him of any infraction that he did in the eyes of H'shem.
pg 427
Nefesh Hachaim
If one finds it hard to serve H'shem with his entire soul, he should focus his Kavana when davening to love H'shem if not with his entire soul, then with as much as he can.
Gate Two, Chapter 15 pg 98