Hope for the best, but prepare for the worst.

To each of us falls a task. And all the Emperor requires of us Guardsmen is that we stand in line, and we die fighting. It is what we do best: we die standing. - General Sturnn, Commander Cadian 412th

"This is General Sturnn of the Cadian 412th Regiment Imperial Guard. Only fools believe that the enemy of my enemy is my friend. Still, the Eldar proved useful enough to bring my men into position, admittedly at cost to their own lives. They lay outside, being cut to the last as I speak. I cannot risk helping them. I will not trade the lives of my men for theirs."
"You will fail this day, General. Without our soulstone the battle will be lost. The Necrons will sweep over you and drink your life out from the hollow vessel of your corpse! Without us you face your doom."
"Eldar! The Cadian 412th have faced doom before. We bested it then and we will best it today! Die well!"
– exchange between General Sturnn and Farseer Taldeer

Well then, I seem to recall a rather pleasant little restaurant not far from here. Care to see if it's still standing? - Commissar Ciaphas Cain

Give any man the power of a god, and you better hope he's got the wisdom and morals of a god to match. There's nothing feeble about my moral line. I value life. That is why I fight to protect it. I mourn every man I lose and every sacrifice I make. One life or a billion, they're all lives. - Colonel-Commissar Ibram Gaunt,
Tanith First and Only

Ogryns. If we time it just right, the Eldar will all be going "What the..." just when what's left of the Company breaks cover over here and piles into them. No spreading out, no fancy stuff, just smash through. Let's see how those degenerate sophisticates handle a healthy dose of pure unreasoning violence. - Commander Fleyitch

I've fought in this endless hateful war for eight months now, night and day. In that time I've aged a decade. My hair has turned grey, nearly all my squad have died, and I doubt I'll ever smile again. I've fought next to heroes and strangled men in their sleep. But I'm still alive and by the Emperor I plan to stay that way.
- Acting-Captain Haines,
47th Armageddon Steel Legion on the Third War for Armageddon