A thoughtful no leaves less confusion than a yes offered only to end the conversation.

The yes that buys peace tends to cost more later. It ends the awkward moment, so it feels generous, and then it becomes a plan someone is relying on, a date in a calendar, an arrangement built around your participation. When it unravels, the other person loses not only your help but the time they spent not finding an alternative. A clear no at the start leaves them their options intact.

When you feel the pressure to agree just to move on, say you need a day. Then answer plainly, without a list of reasons. Being trusted depends more on accuracy than on availability.