Commitment
A publicly witnessed sign-off or pledge to a mission is not too extreme. This has to be more than an empty ceremony. Buttress it with regular "campfire stories" about those who in some way went above and beyond fulfilling the mission. Every culture needs its icons.
Leaders walk a fine line reinforcing the mission. Overdone, it is Mickey Mouse, like giving a scout badge for every little achievement. When a person is outstanding in the estimation of co-workers, it's usually the real thing; little need be said; it shows. The objective is to build a culture in which dedicated performance is not seen as unusual; everyone expects it from each other.