He gave up on it. If and when the shit hit the proverbial fan, Sirius would be the one reacting to it. And James? Chances are he'd take Sirius' side. Peter did whatever the majority wanted. So that left Lupin friendless. It's why he couldn't bare to tell them. To lose everything he had?

The next morning after listening to Sirius curse James out for a good twenty minutes, Lupin finally undid the charm Potter did on Black's bed. The four Marauders headed down to breakfast and it felt like old times again. Maybe Remus could really live two different lives. One with the Marauders and one with Severus. He was still the same person. He just needed to keep the Marauders - namely Sirius - away from Snape.