Trimming the gear properly is the basis for a balanced and relaxed sailing, where you needn't squeeze the blood away from your fingers and feet in an attempt to make rig and board behave as you want. for instance - the harness lines have to be accurately placed, so that you can hang in the hook without having to compensate too much with your hands.

Especially if the wind isn't steady there's a risk that the draft of your sail is moving a lot and consequently keeping your hands occupied.  Many sailors seem to think that an outhaul system is reserved the big formula rigs, but that's not so. As soon as you're exposed for gusting winds, its a relief to be able to trim the slalom or wave sail on the fly to compensate the draft moving.

Perhaps contrary to what you should think it's better to put on a rather big sail for the conditions than a rather smallish sail. Of course it costs a little more effort (and colder fingers) to grab the boom of a little too big sail - but that's nothing compared to being under-rigged. A little too small rig doesn't allow you to lean back with comfort and and let the hook take most of the pull - you've got to work a lot with your arms and hands. And then we are not talking about the exhausting/cold-initiating work connected with slogging and standing in the water to your knees!

Almost the same is valid as to the size of the fin. A little too small fin creates a bad trim, where you have to work too much with rig and board, and even if a pretty large fin might give you certain control problems, in fact that's better than pushing the board away and the endless fight to avoid to loose ground. 

Even if it's most often easiest to waterstart after a fall - sometimes the lack of wind force you to turn to the uphaul line. However, the tired, cold hands and fingers aren't best friends with the pretty small knots of the standard uphaul line. Therefore wise winter windsurfers provide the uphaul line with a kind of thicker knots (or whatever) to give a better grip.

As an extra precaution you can choose to buy a special uphaul line called "Easy-Uphaul" - or perhaps you can imitate the idea and make your own version.

Knots made from small pieces of rope that are woven into the existing knots of the uphaul line. This provide you with better grip for cold fingers and/or gloves or mittens.