Restrain not thyself from doing good

I’m reading the Shepherd of Hermas and (in the translation I have) it is talking repeatedly about not restraining yourself from good. First it struck me as an odd way of putting it, because I’m not used to hearing that.. Then is struck me as odd that it would strike me as odd. There is something weird in our culture that we automatically associate the morally good with something we don’t want to do.