Your no should mean the same thing on Saturday that it meant on Friday.

A refusal given on Friday came from the version of you with a clear head and the whole week in view; by Saturday there is a group chat, a lift offered, and somebody saying it is not a big deal. If your no dissolves under mild pressure, it was not a no, it was a delay.

When you decline something this week, write down the reason while you still believe it. If the ask comes back, you are not rethinking it from scratch, you are checking whether anything actually changed. Usually nothing has except the volume.