Some people are not very kind. They will take advantage of you. Use your good naturedness, helpfulness or kindness to benefit themselves. Do not let these people run you over. They could very well be the closest to you, much older or senior than you, no matter, you need to draw a line and make it clear to them. That you will not allow yourself to be used and abused in any manner. It is best to communicate this at the beginning of any relationship. The next best time is right now, once you realised that you have not done so. Make sure that they understand that you are not to be messed around with, and actually enforce the line that you have indicated when breached. Realise that you essentially teach others how to interact with you by communicating verbally or non-verbally what you will accept and not. And silence is by default an approval. So speak up. Let your voice be heard. Respect each other, and you will have a great relationship.