Have you got a recurring bout of yes-itis? It's very common. You should definitely check. Symptoms include saying "sure I can do that for you" when you want to do it like you want a hole in the head. Can result in a persistent case of burning resentment, with a nasty sensation of burnout and sense of humour failure. May also cause own dreams to be amputated. Can be easily spotted by observing clenched jaws spitting out "I'm fine".
Creating a balance that works for us individually on what we say yes to and what we say no to is important. Too much no, and we are likely to find we have few friends and few fun times as we are so rigid there is little room for pleasure, sharing and spontaneity. Too much yes and our whole agenda will be set by others as we become people-pleasing machines losing sight of our own guidance and goals.
Your yes and your no are YOUR boundaries; where you stand up for you. Where you speak up for you. Where you show up for you. The common confusion is that other people should magically and mysteriously know what these boundaries are without us voicing them. That's a recipe for disaster. It's actually OUR job, not someone else's, to set or verbalise the boundaries on how we spend our time, our energy, our attention. That's ours, and ours alone.
There is a dangerous misconception that if you say NO it means something BAD about you. It means you are not a nice person. Or not a loving person. Or a not helpful person. Or whatever. Actually it doesn't have to mean anything about you as a person. You can choose to drop that fear of judgment that's keeping you trapped in a circle of yes-itis. It's just a SITUATION you are saying no to. It's totally okay. It's a judgment call about the situation, it's not about defining who you are as a person.
If you are finding you are feeling resentful or taken for granted, that is a huge sign. It's a sign that you should be looking at your yes/no boundaries and how and when you verbalise them. There can be a perception, especially for women, that "no" is a sort of dirty word. Actually it's a very powerful part of our vocabulary. It's how we verbally show up for ourselves.