As your friends and family look on, you look into your new spouse's eyes and see your loving gaze returned. The sun shines, the smiles radiate, and your heart wells up with a profound sense of joy and fulfillment. How wonderful it is to have found your 
life mate! You experience overwhelming certainty that you will love this person forever. Should you solemnly vow that you will do so?
The answer largely depends upon on the degree to which you can accurately forecast your future emotional states. Love is, after all, an emotion - and just like anger, despair, or euphoria, it can be insubordinate to our conscious wishes. So what does the scientific literature have to say about people's ability to forecast their future emotional states?
Alas, the news isn't good. Following in the footsteps of affective forecasting pioneers Daniel Gilbert (Harvard University), Timothy Wilson (University of Virginia), George Loewenstein (Carnegie Mellon University), and Daniel Kahneman (Princeton University), dozens of scholars have presented evidence that people are surprisingly inaccurate when forecasting their own emotional reactions to future life events.
Whether people are forecasting their emotional reactions to future election results, football games, or unpleasant medical procedures, their forecasts generally don't match their actual experiences. In one recent study, we and our collaborators examined how accurate people are at predicting their emotional responses to romantic breakup. At study entry, the participants in our college student sample were involved in reasonably serious romantic relationships (the average relationship duration was over a year). They completed an online questionnaire every two weeks asking them about diverse aspects of their personal and professional lives. Embedded in each questionnaire were questions asking them to forecast how distressed they would be (2, 4, 8, and 12 weeks out) if their relationship were to end within the next 2 weeks. Even after breaking up with their partner, they continued completing questionnaires, which enabled us to compare their forecasted distress to their actual distress (for example, to compare the distress they predicted they would experience 8 weeks later to the distress they actually experienced 8 weeks later).
On average, participants significantly overestimated how distressed they would be, and this affective forecasting bias was evident almost immediately after the breakup. In addition, those individuals who made their forecasts when they were strongly in love with their partner were the most inaccurate. They forecasted that they would experience bottomless devastation, but they tended to pull through the breakup more-or-less okay. In fact, they were only slightly more distressed following the breakup than were participants who were not especially in love, despite the enormous discrepancy in the pre-breakup distress forecasts between those who were deeply in love vs. those who were not.
To be sure, breaking up is not fun, and we don't recommend it for weekend entertainment. The results of our study suggest, however, that most people find the distress following a breakup to be significantly less painful than they anticipated it would be, especially if they were strongly in love with their partner when making the forecast. 
What does this affective forecasting research have to do with the vows you should make on your wedding day? It suggests that you should be wary of making promises about your future emotional states. Of course, since "we'll see how it goes" does not make for compelling matrimonial theater, you should instead consider all the things you can promise that happen to be in your control. For example, you can promise that you will always strive to treat your spouse with decency and respect, even when you are angry. Or you can promise that you will never engage in an extrarelationship sexual liaison. These things, and many others that are essential to long-term relationship well-being, are in your control.
But can you solemnly vow that you will experience love for your partner not only tomorrow, but also in 20 or even 50 years from now? There's a decent chance that you really will love your spouse until death do you part, but promising that you will do so seems dangerous, especially if you're the sort of person who takes your solemn vows seriously.
So, tell us in the "Comment" box below: What is the perfect wedding vow?
(This post was co-authored with fellow attractionologist Paul Eastwick.)
