Although many successful givers start from the default of trusting others' intentions, they're also careful to scan their environments to screen for potential takers, always ready to shift from feeling a taker's emotions to analyzing a taker's thoughts, and flex from giving unconditionally to a more measured approach of generous tit for tat. And when they feel inclined to back down, successful givers are prepared to draw reserves of assertiveness from their commitments to the people who matter to them.