Remember: never let them think for you.
When you stop thinking for yourself you become just another weapon to them. If you want to make a difference in the world, if you honestly want to do your duty, remember that you are a human being, just like everyone else. Keep your humanity. Respect your enemy, perhaps, if you can, manage to forgive your enemy, and question those things you know to be wrong.
The rest is up to chance and circumstance. Make the best choices you can, and hope beyond hope you never have to fire a weapon in anger.
~Dune~