A moment of doubt spawns a lifetime of heresy.
Small steps corrupt, brother...

Loyalty and Honour. The two greatest forces that define a man's worth. How a man is remembered is a fine thing to value; but why a man is appreciated is the greatest sentiment of all. The Lion; The Emperor. These were not men as you know them now or how you knew them before you were even made Astartes. The Lion: loyalty and honour. The Emperor: Protector, Deliverer and Avenger.

What more could a warrior of the Imperium require than those 2 priceless ideals?