As Eternity says you can use your syns on a weekly rather than a daily basis if this suits you better but I would always say to have at least 5 syns a day.
For one off events such as a wedding you can however have a flexi day. This is where you plan in advance for how many extra syns you will need to see you through that special day, 40, 50, 60 or whatever. On the day you count your syns as normal but when you reach the limit you set, you stop! Next day you get back on the SW plan with your usual 5 to 15 syns a day and carry on as normal without trying to cut back on syns. You have to accept that you might not lose that week but it is a good way of remaining in control of your eating on those occasions when it is easy just to say 's*d it'.