Keep steady my steps according to your promise,
and let no iniquity get dominion over me.
I can't say it better than this verse. Pray that we are renewed by God's Word, that he keeps our steps steady (as he promises), and that we are not dominated by any sin.
from "30 Ways to Pray for Missionaries," compiled by Elaine Helms for the NAMB. (the full list in pdf form is available here)