Rule of thumb for investment in fundamentally solid stocks: 1. If price drops 10%, just hold 2. If price drops 20%, add 10% 3. If price drops 30%, add 30% 4. If price drops 40%, add 30% 5. If price drops 50%, add 50% 6. If price goes up 10%, just hold 7. If price goes up 20%, still hold 8. If price goes up 30%, sell 10% 9. If price goes up 40%, sell 20% 10. If price goes up 50%, sell 30% 11. If price goes up 60%, sell 40% 12. If price goes up 100%, sell all