BTOB's member Yook Sungjae promoted his positive thinking.

"Not smiling because I'm happy but smiling so I could be happy! Smile smile smile smile! Just smile. Hahahaha," posted Yook Sungjae on his Twitter on Wednesday.

In the picture, Yook Sungjae is smiling brightly for the camera. He is wearing a casual outfit including a black jacket and a black beanie.