Something you once learned to do which is now easy and comfortable to you is second nature. Example: "She started playing the piano when she was very young; now it is like second nature to her." Example: "Wow- you paint so easily!" Answer: "Oh, it's second nature to me. I've been painting since I was a little girl." Some things become second nature because you practice them over and over, others just because you learn them very easily. Example: "It has always been second nature for me to draw with both hands." Example: "Be careful about smoking; if you smoke too much it becomes like second nature and you can't stop."