Amen to the spares.
We were sailing out and about and had a side stay shackle split ring catch on a line and go junk. We didn't know it and the clevis pin came out and went overboard.
It was a real bummer.
Our point of sail kept the mast up but we had no replacement anything.
A fellow sailor in the immediate area became aware of our problem and sailed over and tapes a replacement to his paddle for the in-motion transfer of needed parts.
That helped a bunch.
If we had some extra line, or even a knife to cut some of what we had in the way of halyards or sheets, we could have probably used one or both of our trap lines as temp stays.