"Just... please leave." Peter knew he couldn't stay angry at Padfoot. But he was angry now, and he wanted to make the most of it while he had it. "I can't deal with this right now." It wasn't just Harry that was dragging Peter's various neuroses into his conscious mind, but that had a lot to do with it. It was pretty clear that the girl that Peter thought of as "James' other kid" didn't care much for him either, not that he blamed her.
Hanging around unspoken was the thought that it would all be much easier--his life, his mates' lives, the whole thing--if Sirius had just never found Peter. If he were just sitting at home trying not to be spotted.