No one likes to feel taken advantage of, least of all for being generous.
It is embarrassing and painful.
But it does not mean you should stop being generous, simply that you should be more discerning with your generosity.
Generosity was and is not the problem.
The problem is the persons to whom you are choosing to be generous.
Solve for that, refocus your generosity toward those who truly need and appreciate it, and you will find that your pain and embarrassment will transform into joy and fulfillment.