Clinging has its origin in ignorance, whether it is:

clinging to feeling,

clinging to thoughts,

clinging to beliefs,

clinging to opinions,

clinging to objects (including people and relationships)

Clinging to dogmas,

clinging to desires for experiences (both pleasure and pain). 

Padmapani (1954-), Padmapani is a Dharma teacher, a disciple of the late Ven. Subhadra Goldwater. He has studied and practiced oriental medicine for the past 40 years and is one of the founding members of the the Path to Wisdom project.