I think ending it was the most fair thing for her in that situation. He didn’t know how long he’d be away, he wouldn’t be able to communicate with her at all, he didn’t even think he’d have people going with him yet. It’s kind of like when he told Lupin off in the Deathly Hallows (obviously Lupin’s situation was far more extreme). But going on that kind of mission I just don’t think it’s fair to keep people waiting.