Not everyone will appreciate you. But that can be your own fault. There are people who will take and take and never acknowledge, reciprocate, or say thank you. Or they might say thank you that’s it. Before you get upset and rant, go to the root. Why did you help? Did you offer or were you asked? Was this something you took upon yourself? Were you hoping for recognition or a reward? If so, what was it? Money? Someone’s time? Respect? A friendship? A promotion? An invitation to an inner circle? Be honest with yourself. Because if it didn’t turn out the way you hoped, that is why you feel slighted. From this point on, it is up to you to decide where to go with it. You can speak with the other person and tell them what you thought would happen. That can be uncomfortable, but things will be out in the open. Also keep in mind if there was no discussion of an expectation or contract then the other person may not feel they owe you anything. If you decide to stay silent on the matter, you can make the change within yourself and not go out of your way or do favors for them anymore. But if you continue, the resentment which you build up will be your own doing.