Every yes you give is spent from an account other people are also drawing on.

The committee, the favour, the side project, the WhatsApp group that needs an admin: none of them are wrong. Together they become a full-time job you never applied for and are not paid to do.

Saying no is not rudeness. It is honesty about capacity. I cannot give this the attention it deserves respects a person far more than a yes you resent by Thursday.

Decide in advance what your yes is reserved for, the work and the people and the season you are actually in. Then the no writes itself and you stop improvising under pressure.