Every no you say protects a yes that actually matters to you.

Every yes spends something, and time is the one currency you cannot make more of. Agreeing to the thing you half want means whatever you actually care about gets the leftovers, which is usually nothing. A no is not a rejection of the person asking. It is protecting a promise you already made to something else.

Work out your two real priorities for this month. Measure new requests against those instead of against how empty your calendar looks. Say no early, while it is still easy and costs nobody anything.