There's this older gentleman who would come into my workplace every day for his tutoring sessions.
Every time when I see him for the first time, he would be walking by like there was nothing wrong with him. Where I sit in my assigned spot, I am close enough to smell his cologne. I am glad that he puts a little on unlike some people who feel the need to use up the whole bottle every day.
I've noticed that he would leave few times - up to 6 times in 2 hours. Each time he returned, he would be limping a bit and looking ahead to his seat with a small scowl on his face. I can smell why he leaves frequently - he goes out for a smoke. On each subsequent return trip, his limp would be more pronounced than before and he would walk with a bigger scowl than the last time.
What did I gain from this observation? Smoking is bad for you - you're liable to injure yourself while smoking and you become stressed out thinking about the next smoking session which you know will result in further injuries to you. ;)