Emotional blackmail attempts to control a person by leveraging their caring reputation. Standing up to it requires firmness.
We all get taken advantage of from time to time. Those doing it rely either on power differentials, or a degree of hiddenness in their actions. Fortunately, there are things we can do to correct the balance.
When coping with rejection, people vary in their resilience. But we can all learn to manage ourselves to be aware of our feelings, to be honest but discreet, and to move on if need be.