Years ago, I banned the word "should" as I feel that it creates guilt and obligation.
Ripped off from Yoda, my motto is, "do or do not, there is no should". Policies, procedures and work instructions, particularly relating to Chain of Responsibility and safety, complicates my personal motto somewhat: it is full of "must", "shall", "may" and yes, even "should".
"Must" in documentation means that it is mandatory that the action is done. All the others mean that it is your choice. Guilt and obligation is optional.