Although he had said that, according to Hades, there should be more monsters, Dark Pit was glad there wasn't.

Thoughtless as the Gods were, they had forgotten that he and Pit were connected.
Dark Pit was within inches of his life.

His wings felt like lead, but Dark Pit had already asserted that he didn't need any Goddess's help to fly, and pride wouldn't allow him to go back on that. The chatter of the two Goddesses flew by him, and he tried to focus on their words to keep his mind active. His fight-weary mind was struggling to keep up with the effort of flying, shooting, and dodging; while the chatter made it arguable worse, it distracted him from his own fatigue, and when they were silent he almost gave up on all of it.

The Sea of Souls shined under him, and Dark Pit thought about falling into it and joining the rest of the deceased.
I could see Pit, he thought to himself, we could could be together again...
The grating voice of Viridi brought him to his senses, and he slammed himself against a rocky crag to jolt himself awake. No, I'm not giving up! We will save Pit!

The Sea of Souls seemed to be slowly sucking away what was left of his own soul, and in his delirium he could hardly tell the difference between that and the simple tiring of his wings.
What the hell is a shadow when there's no one there to cast it? A reflection without someone to reflect it?
Stubbornness and fear alone drove him on, allowed him to stay conscious when his other half could not.