A calm mind is difficult to manipulate.

Manipulation works through urgency and emotion, by producing a state where you decide quickly and feel that you must. A settled mind is a poor target because it takes the time to check, and checking is exactly what the pressure was designed to prevent.

When you feel rushed toward a decision, treat the rush itself as the signal. Say you will answer tomorrow. Almost nothing genuinely requires an immediate answer, and the ones that do are rarely the ones that benefit you.