I sometimes kept my door shut as a teen because our cat Peasant kept snuggling against me- I couldn't sleep with her hogging the bed. If she had just gotten in bed with me, but not crowded me, it would not have been a problem, but I had insomnia issues then to begin with (and still do). It was hard enough to concentrate in class.
But I still miss the sound of her feet late at night, and then seeing the silhouette of her head as she paused at the door, peeking in.