Judging from the last couple of years on here, the most stressful things for most brides are:
1. Guest List worries. And managing table plans diplomatically.
2. Pushy family trying to get you do to what they want or trying to take control of the planning. Especially if they are paying for any or all of the wedding.
3. Indifferent or unhelpful bridesmaids.
4. Finance.
5. Pregnancy (own, or bridesmaids, MOH or close family).
6. Competition from other brides- eg H2B's sisters planning weddings just before yours and 'stealing ideas'.
7. Feuding family members- people saying they won't come, or bride's family not getting on with groom's family.
8. Pressure to invite kids.
9. People forcing their kids on you whether you like it or not (eg buying flower girl dress when kid hasn't been invited to be flower girl).
For most of the above, the coping technique will vary according to the specifics of the problem, as will any 'stress management technique'. Some people will grab the bull by the horn and wade in to sort out the problem. Some will retreat and put the problem off. Some will give in and just fume or stress about it before the wedding. Mostly we try to give advice on here but I'm not sure about any stress management techniques other than 'take a deep breath'.
Hope this helps