You can love your family and still need a closed door sometimes.

Needing time away from people does not mean you have stopped loving them. Closeness and solitude pull on different parts of you, and filling one does not fill the other. In a full house, wanting the door shut can feel like a small betrayal, so people stay in the room and get quietly short-tempered instead.

Try saying it plainly before you need it: an hour upstairs, then down for dinner. Most families take that better than a snapped answer later. If a door is not an option, find the equivalent, a walk, a long shower, the back step. The point is that you come back, not that you never leave.