Steady:
1. Not easily disturbed or upset
2. Constant in feeling, principle, purpose, or attachment

“Why does it even matter if people get suspicious?” Harry lay back and stretched, and Severus watched him do it. He was almost cat-like, with an unselfconscious grace that took him off guard each time he saw it. It was how he looked on a broomstick. The absolute master of his body. Harry looked over at him staring, and smiled.

Oh, that smile.

Unguarded. Uncomplicated. Free, and easy. It made Severus feel drunk with power to put an expression like that on his face. He lifted one of Harry’s hands to his lips and kissed his knuckles. I love you, he thought. It was becoming almost routine, thinking that. I love you. Almost normal. Almost tolerable to hold in his mind, now.