It was ecstasy and agony. Tom had not imagined resurrection to be so painful, so full of regrets. He had read that to re-absorb a Horcrux, one needed to regret the death that had created it. But it was hard when feeling righteous for killing his traitor of a father or grandfather for abandoning his mother. Still, he wanted to be whole, so he tried. With every Horcrux that returned to him, he felt more remorse. Nagini gave up her soul-shard easily. The cup put up no resistance either. Then the diadem and the locket were absorbed. It was more challenging with the ring because he had hated the old man with all his heart, but in the end, it became nothing more than a worthless trinket on his former enemy's finger. Lastly, he started to pull on the shard of the lightning bolt scar that adorned the "Boy who Lived's" forehead. The tiny fraction of his soul slipped out, but when it came to the remains of the diary, the young man put up a fight. Livid that the ritual refused to complete, Voldemort started to pull with all of his soul until the battle of wills had him lose consciousness.