Rejoice with those who rejoice

One instance in Descent Into Hell that I tried to make sense of, is when Wentworth reads in the paper that Aston Moffatt has been knighted. "Wentworth knew he could share that pleasure... with a perfectly clear, if instantaneous, knowledge of what he did, he rejected joy instead. He instantaneously preferred anger, and at once it came; he invoked envy and it obliged him" (80). This situation reminded me of the command found in Ramns 15:12 which says, "rejoice with those who rejoice, mourn with those who mourn." How many of us actually conciously do this? When I rejoice in the sucesses of those around me, it is because I honestly and naturally feel happy for them inside, not because I analyze the situation and make the decision to be happy along with them. At least I don't think so. But Wentworth's situation gives the idea that it is a concious choice. As a fellow historian, he certainly had reason to rejoice in this accomplishment, if not for Moffatt personally, at least he could at least rejoice in the honor paid to the field of history. However, he chooses envy instead. He could have chosen to focus on the joy, but he didnt. I wonder: am I missing out on joy because I don't deliberately look for reasons to rejoice with others? Or is Williams wrong to turn something spiritual and emotional like joy into an alternative to be chosen through logic and (instantaneous) deliberation?