When you give abundantly of your time, love, energy, and resources without receiving an equal exchange of energy or appreciation in return, over time you will build resentment. You may think it’s directed at the other person or the group, but in fact, it’s more about you being upset with yourself for not speaking up or not drawing stronger boundaries.
Remember, no one will value you unless you value you. Don’t make excuses for them and wait for them to show appreciation. Start by gracefully speaking up and sharing your feelings, in case they haven’t noticed what you are doing. If nothing changes, throw a chair at them and see if that helps (just kidding). It may be time to change the rules of engagement.