You are at a place like Whitstable or Pevensey Bay, getting ready for a race. The tide is low, but coming in, and it is quite windy. You don't want to launch too early and tire yourselves out before the start. Also, the longer you delay launching, the more the tide will come in, so you won't have to walk quite so far down the beach. As a result, when you finally decide to go, you are not exactly late, but you have no spare time.
You dump the boat in the shallows, and while your crew takes the trolley back up the beach you unroll the mainsail and shackle on the halyard. Or rather, that is what you intend to do, but at the critical moment when the shackle is open something happens. Maybe a gust of wind, a larger wave rocks the boat and puts you off balance and splash the shackle and/or pin fall into the sea. The chances of finding it are practically zero.
Now what do you do?
If you are not prepared, you are in trouble. You have to wait for the crew to come back, then dash up the beach to get a spare from wherever you keep them. By the time you get back several minutes have elapsed and you may be late for the start. It is much less effort to reach into the boat to the place where you know there is a spare shackle, and get on with rigging the boat! Even if there is no spare shackle, you ought to have a piece of cord handy and be able to use it to tie the headboard to the halyard.
Although dinghy fittings are much more reliable than they used to be you have to face the fact that occasionally something will fail in some way. With a bit of forethought you can minimise the effect of any breakage, make some running repairs and complete the race. At the very least you ought to be able to get back to the beach without requiring assistance. So, make sure you carry a few spares! I always have a couple of shackles and a length or two of cord. If your shrouds are attached using a clevis pin and safety ring you ought to have a similar spare as well. Believe me it isn't funny if you look under the boom and see the leeward shroud dangling in the water! If you can't catch it and reattach it you are in trouble.
Having dual controls for the kicker, loose foot etc. is a useful bit of redundancy. If something breaks on one side of the boat you should be able to knot it up somewhere and continue with a one sided control. Furthermore you also have the possibility of redeployment. It would take me very little effort to detach my Cunningham control from the mainsail and attach it to the outhaul or kicker - and I know which control I would rather have!
So, maybe during the long winter evenings you can exercise you mind imagining ways to fix unexpected gear failures. For example:
Kicking strap. If you have an eye under the boom and this breaks you have a problem. You can tie something round the boom, but unless there is an eye or hook somewhere the lash up will slip forward. You could prevent this by having a second lash up pulling this loop towards the outer end of the boom. Do you have enough spare length of cord to do this? Better to have a hook or two on the topside of the boom.
Clew attachment. If this fails the mainsail turns into a large uncontrollable flag and in any reasonable breeze you will have to lower it before you can make a repair. Why not do what I do and tie the clew to the boom with a piece of cord that circles the boom and goes through a small eye? If the shackle or the outhaul control fails this cord will keep the sail under control.
Rudder downhaul. At Brancaster this year a rather unfriendly wave dumped the back of the boat onto a sandbar and the downhaul broke. This made life tricky, but not impossible because I have a big wing nut on the pivot point as well and after pushing the blade down and tightening it, it would at least stay down while going to windward. Downwind it would gradually come up and we had to stop every now and then and put it down again - but at least we were able to finish the race!
Tiller extension. If the joint fails you ought to be able to tie it back on somehow. There may be a lot of play, but surely some sort of control is better than none? It has just occurred to me that the spare jibstick that I carry - in case the mast mounted one fails - that so far has been used as a weed removing stick and a punt pole, could also make a spare tiller extension!
Toestraps. If the anchorage has pulled out - surprisingly common on new boats - put a foot under the thwart or [for the crew] the cross strut at the front.
Apart from having several lengths of cord on board to let you make any running repairs, you need to think about what sort of knots you might use. 6mm dyneema is as strong as 2.5mm 7 x 19 wire, so can hold up a mast if necessary, but it is not easy to tie binding knots in it. Some 4mm polyester cord is needed as well. Maybe you could spend a few more winter evenings practising knotting?