Karma - The Mechanism: Tattvarthasutra 9.16

Vedaniye shesah (16)

All other obstacles are manifestations of karma that determines our feeling of life. (16)

This is hunger, thirst, coldness, heat, annoyance by insects, the craving for stability (homelessness), the fading of our intention to grow, illness, pain and lack of sincerity (the spoiling of our intentions).