I had a quantified-self binge about 2 years ago, and many of those practices have stuck with me. One app I still use encourages me each night to reflect on my day with a mood rating and writing a short note. One of my favourite features of this app is that, attached to my nightly reminder, is a note I left from some time in the past. I only have about a year and half of data, but I’m reminded of so many moments that I’d probably have never otherwise recalled.

I’m reminded of days I spent getting assignments done late at night, and evenings I spent on the town with my friends. I’m reminded of really nice dates eating delicious dinners and seeing mesmerizing movies, and the nights I spent alone eating pineapple and watching Netflix. I’m reminded of days I spent in Toronto, Seattle, abroad and at home. I’m also reminded of days where I ended up feeling pretty crappy, and I get to think about why that was.

Our memories are unfortunately limited, unpredictably plastic, and affected by all sorts of cognitive biases and emotions. When we think back, we are likely to recall events differently, and sometimes memories change over time. The feeling and the colour of a time you spent with a friend is often dependent on the state of your current relationship with that friend. A funny story that happened on a night out gets exaggerated each time the story is retold and refined. A diary with timely entries helps you reflect on events as they happened, in the context they happened, and gives you a fuller picture on the fluctuations of your attitudes, relationships, and feelings.

When you look back in a diary, you realize the variety of experiences you go through. We might never fully understand how enormous of a variety that is, because we so often think about our immediate situation, but it gives incredible perspective on how amazing each individual life can be. To think that everyone you pass in a crowded street, or everyone sitting silent on a city bus, has such magnitude of experience and personal depth. And that experience grows at least linearly for each year you’re alive.

This leads me to think about the over 100 people killed in Paris last night. Their families and friends are suffering a great loss. There are thousands of people whose lives were likely uniquely touched in some way, however small, by the victims of those attacks. Our world now lacks the richness of combined thousands of years of beautiful human experience.

I think sometimes our present bias causes us to ignore how vast human life really is, and it’s important to reflect on that when attacks are made on it. I think understanding the richness of life is an important key to peace and humanity.