Some people will bleed you dry. Take and take, with no regard. Asking of you what is beyond reason without limits, remorse, or thought. They cannot see anything past their own needs. You are simply a means to an end. They do not appreciate anything and will never repay you your kindnesses. They are entitled without earning it. They don't owe you anything, the world owes them.
Association with people like this guarantees you to be used and abused. They have week morals and no sense of self or respect, no conscious to keep them in check. You are not like these people. Do not lower yourself to their level, you are a better person than they can ever be worthy of. Remember your path, and walk it. Never be afraid to stand tall and stick up for yourself. These people have no boundaries, build your's strong and resilient. People who abuse your kindness aren't deserving of it. If you always have to put up your guard to protect yourself, it is easier to simply cut them out/off; that is the only thing they truly deserve from you. Enabling them is an injustice one which they will never learn from.