Admit it or not, many members of the Reapers could clearly see the stark contrast in their lives before and now. In the days preceding Hera's demise, every waking moment seemed like a ceaseless revelry, albeit not of the enjoyable type. Peace eluded them entirely. Genuine, enduring peace had been a rare occasion.
Hera's departure left an agonizing void, a hollow in their hearts that remained untouched by anyone or anything else. This is precisely why they mourned her loss for as long as their memories could stretch. Yet, her absence also exposed them to a life devoid of her presence. Hence, having her back and everything restored wasn't an unmitigated cascade of rainbows and butterflies.
"I may have you now, but I no longer have complete dominion over the Reapers," Heaven lamented with a heavy heart. "No matter how hard I try, I will never succeed. Not in this body. Not as Heaven Liu."