We sometimes think that everything was much better and easier in the past. It's one of the tricks our minds play on us, especially when we are in low spirits.

Actually, it's unlikely that things were objectively better in the past. This form of thinking is calledrosy retrospection, which is a well-studied cognitive bias. It happens because when we think about the past, we are more likely to focus on positive generalities than annoying details.

If you think back to a holiday with your family five years ago, you're likely to recall the beautiful views rather than the uncomfortable bed. In other words, the negative details disappear from our memory over time while the positive ones remain.

Rosy retrospection can influence how we make decisions, and it's one of the reasons why we easily return into problematic relationships. The longer it is since we experienced the negative influence of a relationship, the more likely we are to let the good memories outweigh the bad memories and to perhaps forgive unforgivable behavior. It's always a good idea to review our nostalgic (怀旧的) feelings with a healthy degree of doubt.

But rosy retrospection does serve an important purpose. It keeps us in a positive state of mind in the present and is important to our psychological wellbeing. In fact, people who tend to remember negative experiences more than positive ones are likely to exhibit psychological disorders. Research generally suggests that our happiest days are still to come. And even if they're not, it's still important to believe that they are. Don't shy away from looking upon the past with a certain degree of nostalgia. But, for the same reason, don't use the past as an excuse to be unhappy in the present.