Thanks. 40 feels a lot like 39.
It's not, though.
One day very soon you won't be able to read your prescription bottle. The newspaper will start printing very small letters. The text on your phone will shrink.
Meanwhile the things you eat will suddenly make you feel queasy. You won't be able to hold or handle things like you could at 39. You'll start to have random, unexplained pains in parts of your body you didn't know existed. The time span between "I have to shit" and "Oh SHIT, I have to SHIT" will decrease. Same with pissing. If you're lucky you won't leak a little.
It's a conspiracy. They all know when you turn 40 and do that to you on purpose.