SN 22.7 Upaadaaparitassanaa Sutta: Grasping and Worry
A normal uninstructed person regards body as the self, the self as having body, body as being in the self, or the self as being in the body. Change occurs to this man’s body, and it becomes different. Because of this change and alteration in his body, his consciousness is preoccupied with bodily change. Due to this preoccupation with bodily change, worried thoughts arise and persist, laying a firm hold on his mind. Through this mental obsession he becomes fearful and distressed, and being full of desire and attachment he is worried.
This is also true of feeling, perception, mental formations and consciousness.