Time

This is the one resource that everyone has in equal measure. We hear ourselves & others say "I don't have time." Lucius Annaeus Seneca, a Stoic philosopher of Ancient Rome said "We fail to treat time as a valuable resource, even though it is arguably our most precious & least renewable one." And that last part is the key, any moment in time lost, is gone. It's a different thing to opportunities (which is some good news, as opportunities can present themselves time and again). There can never be an exact moment you are listening to this ever again, even though you can listen to this some other time, again and again. I believe you get the idea. You'd find this insightful. Enjoy it.