In his book Stumbling on Happiness Daniel Gilbert writes that we are better off assessing our happiness in the moment than trying to predict what will make us happy in the future. Based on a concept he refers to as presentism, we have a difficult time trying to imagine a future that is much different than our current situation.
Gilbert says we find it difficult to imagine thinking, wanting, or feeling differently than we do in the present moment.
Additionally, because our brains are unable to retain all of the details of what happens in our memory, it retains pieces of our experiences and when we recall a memory, our brain fills in the holes, using our current situation as a reference. As a result, we often wrongly predict future emotions or feelings.
The other challenge with predicting happiness is we wrongly assume that positive events will always make us happy and negative events will always make us sad.
In his book, The Happiness Hypothesis, Jonathan Haidt explains this common misjudgment is due to the adaptation principle.
When we think about all the good things that could happen to us, or all the bad things, we tend to project how we believe we will feel if those things happen. Not surprisingly, we predict we will be happy if good things happen and we will be sad if bad things happen. We assume positive things will make us happier, however studies show this is not necessarily so.
Haidt writes that regardless of what happens we tend to adapt.
He points out that lottery winners and those who suffer accidents resulting in paraplegia both pretty much return to their baseline level of happiness within one year. That means we adjust to our new situation, and the luster, or the pain, diminishes. This could explain why we keep striving for more. It may be an effort to sustain our happiness at that higher, yet fleeting level.