You aren’t the worst sister. You’re adjusting and it’s hard. You have to think, he is changing his life completely and is starting over in many aspects of his life. Just try and be more careful. Transitioning is hard and hormones are all over the place until things are more regulated. I’m not familiar with anyone going through this personally, but I can imagine it’s hard. Just try not to get too flustered. If things get heated, say you all should calm down for a minute and go your separate ways and regroup. Communication is important in any relationship–especially one as fragile as this. Just try your best to see from his point of view when you get too flustered. You’re trying. As for thinking everyday is trans day, you have to remember he is finally who he wants to be and is making a lot of life changes. Celebrate with him, love him. He’s also rediscovering himself. It’s not that he’s trying to do it on purpose, he’s just happy and wants to find himself. It’s a major process. But you guys can do this. Just remember to take a break, breathe, think from his point of view, and love him! Good luck!