Sunk costs are a gift from the past.

In the past you spent some resource, usually time or money, on something that cannot be refunded. Now, in the future, you must decide whether to accept this gift from your former self.

A few years ago I was trying to sell my bookshelf on Facebook marketplace. It was my bookshelf for the last two years and I had become quite fond of it. That day I spent over two hours packing the books into boxes, wiping the shelf down, taking multiple photos, writing up an ad then posting it. I listed it as $50.

Within a few days it was clear that nobody was willing to pay that much for a second-hand bookshelf and thus I grudgingly reduced the price to $20. After a week, still no responses. Then $10. Then $5.

The first inquiry I finally got was one month after the initial listing. It was from a lady who wanted to come inspect it at a time I would be in class. I asked my housemate if he would be home at that time to let her in. He said no – he was working. I began to panic at how to manage this situation.

My housemate, noticing my distress, asked how much I was selling it for. $5, I said. He laughed for a long time. And that’s when I realised the ridiculousness of my situation.

If somebody rocked up at my door and told me to sell a second-hand bookshelf for $5 I would say no. $5 is not worth the time and effort. I could try and get creative – sell it at a higher price or build something new perhaps – but the easiest option is just to get rid of it. The best form of productivity is elimination.

But because I had invested all the time and effort into the bookshelf I convinced myself that it had to sell. That somehow, my efforts of cleaning, photo-taking and ad-writing and its sentimental value over the last few years suddenly made it more valuable. This was, of course, delusional.

The problem with sunk costs is that situations and values evolve over time. Maybe a month ago, $50 for the bookshelf was worth the effort of advertising, but not $5. The situation evolved. And maybe a month ago, there was nothing much going on, but now exams are coming up and time is more precious. The values evolved.

Sometimes sunk costs are a gift. Having written 350+ blog posts is a pretty good incentive to keep going: it would be a shame to lose it now. This is where tracking habits and accountability partners can shine. Past investment is a motivator for future effort.

But evaluating sunk costs requires a constant erasing of the past and analysis of the present. If one day I don’t find writing valuable anymore, I would stop writing, regardless of all I had written previously. The same goes for toxic friendships, boring jobs or destructive habits. Holding onto gifts just because of guilt is a tragic irony: you waste even more time by not letting them go. And time, being the only finite resource we have, is the worst thing to waste.

Evaluate your gifts carefully.