The person who says yes to everything may be making promises on behalf of their future exhaustion.

Agreeing is cheap in the moment and expensive on the day. The version of you being volunteered lives weeks away, has no voice in the conversation, and is imagined as rested and free, which is why it feels generous to say yes now. The bill arrives later as resentment, cancellations, or a favor done badly, and none of that was the intention.

Before accepting anything, look at the actual week it falls in and picture the evening before. Ask whether you would take it on if it started tomorrow morning. If the honest answer is no, say so now, while declining is still small rather than a late withdrawal.