It appears attachment is the root of all mental agonies; it is attachment that makes every creature miserable and brings on every kind of woe.
मनसो दुःखमूलं तु स्नेह इत्युपलभ्यते। स्नेहात् तु सज्जते जन्तुर्दुःखयोगमुपैति च॥